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How are drugs distributed in regards to bone marrow?
I know that as volumes of distribution increase they correspond to the blood, then the vascular rich group (heart, kidneys, liver, brain if BBB permeable), then muscle then adipose. But things like flow should also be taken into account. So are drugs usually distributed in a similar manner to blood, vascular rich group, etc?

I guess this is about the distribution of a drug within the body?

Volume of distribution is a property of the drug and not the tissue. Your question is unclear.

Thank-you for letting me know, but can you explain further? I know that the volume of distribution is unique to a drug, but high volumes of distribution indicate the drug is preferentially stored in adipose; and that low volumes indicate it is retained in the blood. I am asking where the bone marrow would fit in the progression above. i.e. Are low Vd drugs stored in blood AND bone marrow? or Does the bone marrow retain drugs with a similar capacity to the VRG?

@RobyVicary Vd is an indicative of the drug solubility. Drugs with high water solubility are enriched in blood whereas the ones high lipid solubility (and hence low water solubility) end up in adipose. There are other factors too apart form solubility. However, pharmacodynamics is not simply determined by drug solubility. Your question should be rephrased and perhaps you should ask how much percentage of a certain drug in blood is present in bone marrow. Most bone marrows have good vasculature; so I would guess that bone marrow should have almost the same concentration as the blood.

How are drugs distributed into any tissue, and what affects it?
Note that there are no general answers, and that this is highly dependent on the drug in question.
Active or passive transport
Is your drug a substrate for any uptake or efflux transporters that may affect the distribution?
Solubility
Lipophilic drugs will generally have a greater volume of distribution, as there is more passive diffusion into tissue.
Blood flow
How much drug is presented to the area in question? Tissue with greater perfusion (e.g. kidneys) will have a greater exposure to the drug. Look up the well-stirred model.
Relating this to the blood marrow
So what should you research in order to answer your question?

What are the physiochemical properties of the drug in question? How are these compared to other drugs where the bone marrow is a target?
Is the drug a substrate for any relevant transporters in the tissue of interest?

You should also look up if there are any physiologically-based pharmacokinetic (PBPK) models for your drug or drugs with similair physiochemical properties. Some of these are free, and allow you to make general assumptions about the distribution of the drug.


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What proportion of lung compliance is attributable to alveolar surface tension?
I am reading Guyton and Hall, chapter 38, Pulmonary Ventilation. It states that the two main factors influencing lung compliance are 1) tissue elasticity 2) surface tension elastic force. An experiment is used to illustrate that one surface tension requires far more pressure to overcome during respiration than tissue elasticity, see diagram.
The text then states that because the pressure difference in the normal lung is about three times greater than the saline-filled lung (which has no surface tension effect, only tissue effects) that one can say that lung elasticity is only about one third tissue elasticity and two thirds due to surface tension elastic force.
My question is that given lung compliance is the reciprocal of lung elasticity does this mean that lung compliance is more due to tissue elasticity?
"Lung compliance is the volume change that could be achieved in the lungs per unit pressure change. [Lung e]lastance, also known as the elastic resistance is the reciprocal of compliance, i.e. the pressure change that is required to elicit a unit volume change. This is a measure of the resistance of a system to expand (Kahathudwa 2022)."
References:
1:
[2] https://owlcation.com/stem/Lung-Compliance-and-Elastance
[3] Guyton and Hall Medial Physiology, Chapter 38.
[4] Stat Pearls, Pulmonary Compliance, https://www.ncbi.nlm.nih.gov/books/NBK538324/

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Do dead cells always contain no nucleus?
If I examine a dead cell, can I be sure that it has not a nucleus?
And what about the other organelles?

If you're looking at cause of death by standard apoptosis, to initiate the process, cytochrome c will be released from the mitochondria, bind with apaf-1, and undergo a structural change resulting in what looks like a biochemical ninja star (figure 4). This will activate caspase-9 which will activate other executor caspases, eventually creating an avalanche of protein-degrading enzymes that will leave the structure and organelles of the cell looking like paper mache. Regarding the nucleus, the complexes of enzymes meant to maintain dna integrity and structure will be degraded, the DNA's network influence on the cell will become largely inert, and the dna will be condensed and broken apart by nucleases. The membrane of the nucleus is full of proteins and ribosomes, and these will be degraded too. If you are looking to simply identify an inert nucleus by its skeleton, you may not have much success either - here are a few good images from a nice study showing the progressive destruction of a nuclear structure.

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What are the best plants to cultivate yeast from?
I know that cultivating yeast from potatoes yields a good brewing yeast and that forms of wheat make good baking yeast, however; I have not seen much information on other useful plant yeast cultures. What are some of the other plants that offer potentially useful yeast cultures?
*edit : corrected my error in thinking yeast was produced by plants due to a answer given

Are the wine-producing yeasts that live on grapes too obvious?  (FWIW, the plants do not produce the yeast.  Yeasts are independent organisms which colonize the surface of some plants, among many other things.  But they, and other fermentation-producing organisms, can be found elsewhere.  See for instance sourdough bread.)

Grapes are a bit obvious but it follows the main idea of my question. I'm curious about plants that are not commonly used. There isn't a directory that I could find that lists yeast cells commonly fond on specific types of flora

Yeast colonize the surface of many plants — for example they are a typical part of the normal surface flora (microbiome) of fruits such as grapes1 and pears2.
As you can see from the second reference, yeast can compete with other microorganisms to delay rotting of the fruit.
You might also find the "Uses" section of the wikipedia article on yeast and this article on winemaking to be of interest.
References:
1: Zahavi, T., Droby, S., Cohen, L., Weiss, B., & Ben-Arie, R. (2002). Characterization of the yeast flora on the surface of grape berries in Israel. VITIS-GEILWEILERHOF-, 41(4), 203-208.
2: Benbow, J. M., & Sugar, D. (1999). Fruit surface colonization and biological control of postharvest diseases of pear by preharvest yeast applications. Plant Disease, 83(9), 839-844.

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How would you find and cultivate specific forms of algae?
Knowing how simple and efficient it is to grow algae, I started wondering how a person would specifically isolate and grow different strands of algae. Say I walk to the closest body of water and took a sample of water. How would I prepare it so that I only got a specific strain of algae, say a green algae?

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Meiosis and combinations of chromosomes
I was pondering about the genetics of siblings. It occured to me that a pair of biological brother and sister (not brothers or sisters) could inherit completely distinct sets of chromosomes from their parents, the mathematical probability being $\frac{1}{2^{46}}$.
This calculation is based on the assumption that each pair of chromosomes, upon meiosis, get separated independently of other pairs. Do you think I’m right about that? Has anyone looked into this matter? Could it be that a chromosome prefers to be accompanied by a specific chromosome (in a pair other than its own) during meiosis?
Edit: I only have a high school level understanding on this matter and I just realized that my speculation directly contradicts Mendel’s law of segregation. But as pointed out in the comment on the answer, some wiggly interaction might interfere with the assortment with some peculiar genes, although it doesn’t mean that some chromosomes are more fond of each other. Close the case.

It would be right if there were no recombination (see also crossing over) and no new mutations. However, there are crossover and there are mutations and hence the calculation is wrong.
Segregation
You have solved this problem yourself. You assumed that chromosomes segregate perfectly independently which is a rather sound assumption. The probability is $\frac{1}{2^{46}}$
Recombination
Assuming a genome-wide recombination rate of 22.8 (Wang et al. 2012) and assuming that the number of recombination is Poisson distributed, then the probability of no recombination is $e^{-22.8} ≈ 1.25\cdot 10^{-10}$.
Multiply this number by $\frac{1}{2^{46}}$ and you get about $1.8 \cdot 10^{-24}$. I would note however, that the assumption that the number of crossover is Poisson distributed might not hold (even if it is how it is typically modelled)
Mutation
Now assuming a genome-wide mutation rate of 45 (Rhabari et al. 2016), and assuming that the number of mutations is Poisson distributed, then the probability of no mutation to happen is $e^{-45} ≈ 2.9 \cdot 10^{-20}$.
Hence the probability becomes $\frac{1}{2^{46}} \cdot e^{-22.8} \cdot e^{-45} ≈ 10^{-44}$.
Note that we assumed that the number of mutations and the number of crossovers are independent which is definitely wrong. If we were to know the correlation, we could make better estimates. This would bring our estimate to some higher probability.

Whoa, I never knew that recombinations are so likely. And I believe you’re talking about recombinations between pairs and nonpairs of chromosomes, which does make my assumption false. Now let me elaborate: apart from recombinations and mutations, could there be any tendency of certain chromosomes from the same parent or whatever ‘like’ each other, going hand in hand in meiosis? Maybe it’s a silly question.

I think chromosomes segregate completely independently but I am not sure. Also, you might want to read about meiotic drive.

That looks like exactly what I was looking for!


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Can all animals breathe manually?
Originally I was pondering about why we have the ability to breathe manually. I couldn't think of any tangible advantage, given that the body can develop mechanisms to regulate the rate of breathing when needed.
An uncited source (on reddit) said "any animal that can vocalise 'can' breathe manually." Is that true?
Secondly, do non vocal animals, for eg., some arthropods, not have any conscious control over their rate of breathing?

Are you talking about slowing breathing if they are trying to be stealthy, or vocal communication?

@James any form of manual/forceful inspiration/expiration. I interpreted the answer (on reddit) in the sense that being able to control breathing is a necessity to be able to speak/vocate; although I'm not very sure. Just wanted some more insight into the matter.

Could you link to the Reddit? This site works best when the questions are specific and answerable.

https://www.reddit.com/r/explainlikeimfive/comments/2b927k/eli5_can_animals_breathe_manually_or_are_they/

I think I see the problem. You need to properly define what breathing manually is. For example, a bird may have to control its breathing to sing, but may not willingly hold its breath per se. Would that count? Any dog owner knows dogs will restrict their panting as soon as they see a squirrel or equally chasable critter. Would that count?

Some mollusks have lungs and can use breath for nest building, defense and diving. They have 100 times less neurons than arthropods.
semi-aquatic insects can control air for going under-water, and some spiders, beetles and spittle-bugs can control bubbles. There are even shrimps that snap at water to produce bubbles.
Fish can hoover and squirt out targets using gulps, without even having lungs, build bubble nests and they also have a swim bladder that they can use to control buoyancy. Human lungs and fish swim-bladders are thought to have evolved from primitive fish that gulp air: https://mainichi.jp/english/articles/20160819/p2a/00m/0na/004000c
It illustrates early vertebrate control of breath-like mechanisms. It's sometimes their main mode of interacting with objects and prey.
Some reptiles hold their breath under water and use bubbles, i.e. iguanas, water anoles and crocodiles. Some reptiles can vocalize, i.e. gecko's : https://www.youtube.com/watch?v=0Q_1KW0Q-10
Scientists don't think that they have much conscious thought.
Amphibians can hold their breath for long periods to swim and use the throat to hoover prey, and most frogs can vocalize: https://youtu.be/y7F0ObBiHio
orang-utans can blow bubble gum, swimming birds and mammals can often do a lot of bubble stuff.
Perhaps the truth pivots on knowing what animal consciousness is, which is amply debated on the web.
Manual involves hands. Consciously and voluntarily involve thought, and those are the words used in biology.
Animal will and conscious reasoning is one of the most controversial topics in science, and scientists still argue both ways, because they CAN argue, and there is no agreed measure of consciousness.

showing invertebrates posses something does not preclude a group of vertebrate lacking it. Some insects also have wings and parental care. breathing control is not hard to evolve so it could easily evolve multiple times.


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Career advice for a bachelor of biology with russian STEM diploma
I'm from Russia. I majored in biology(genetics), wrote a bachelor's diploma in the field of psychogenetics, and graduated with mean grade of roughly 4 out of 5. Back then some circumstances arose that prevented me from an academic career (including lack of biotech companies in my area), so I had to make do with an entry-level job. Biotech companies in Russia can afford to be picky and hire only experienced staff even for an entry-level position such as lab technicians. With a lot of people in the field looking for a job, and a few biotech companies, I don't have a lot of chances there.
I've heard that Russian diplomas in STEM fields are valued abroad, probably more than they are in Russia; that brings me here. What are my chances of finding positions as a junior lab member, lab technician, etc. in a biology-related field overseas with my higher education diploma and practical experience (achieved during two years of lab work in the university)? What skills/qualifications do I need to get to improve my chances? What direction would you suggest to start my research on possible employers? Could you give me any further tips on career track?

Are you interested in graduate school? I know America has a lot of biology BS lab techs. A Ph.D. program might be an easier way to getting your foot in the door overseas, if you're willing to put up with an extra 4 - 6 years of schooling, and your job opportunities with a Ph.D. might be better. If you speak English as well as you seem to write it, your language skills are probably fine. I don't anything about the job situation in Europe though.

You might be interested in reading Paula Stephan’s book: how economics shape science ( talk: https://www.healthra.org/download-resource/?resource-url=/wp-content/uploads/2013/08/Stephan_9_2012.pdf ). In short, the general problems with biology unfortunately are global; p.s.: Switzerland or Germany are quite strong in biotechnology, and not even overseas

You may be able to get a position as a lab technician in Europe, but otherwise in most places you'd need to do a Master's as well. There are plenty of pharmaceutical companies in Switzerland but I am not sure on the qualifications required for an entry-level position. I'd suggest that you build your skill-set around the position you want. You haven't said anything about what you would like to do.

In my opinion this is a general problem throughout the life science industry all across the globe. Personally I work in the UK and although I am now in a slightly better position, the beginnings were tough - very tough (despite having a MSc). The money still isn't great but not as bad as what it was during my first two years.
I do have quite a few friends in Germany who tried to establish themselves as scientists there, very few did. Most ended up pursuing careers in Life Science Sales are something else all together. I am not saying you can't make a living in the life sciences but it's hard

There are quite some positions offered in bioinformatics, but I think they often require at least a master diploma. That being said, you can learn a lot by yourself using online resources. So if you have time, you might try to follow some online course (for instance on coursera or edX) to see if this is a kind of career that could suit you.

I'm voting to close this question as off-topic because it is not about the science of biology.

maybe try Academia.stackexchange?

You have so many questions, and it seems like you have no idea what to do next. So you better ask Russian guys who are really into this as

Good FAQ with a lot of cases from real life:
https://vk.com/career_in_biology
More like Career in Biology 101:
https://vk.com/science_career (also they have a chat in Telegram)
Career adviсe and pretty decent list of positions: https://blastim.ru/
Winter biotech school (in my opinion you have good chances to get there as they do it for people just like you): https://vk.com/futurebiotech
Completeish list of biological summer schools where you can get hands-on experience: https://vk.com/coolresearch


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What is a Slurry in Microbiology?
I have been reading this article and they refer to this thing called 'slurries' that can be made from soil samples. This is in the context of being some sort of microbiological method.
"slurries can be made from these soil samples"
Does anyone know what this is? When googling it, I can not find a clear answer to what the method does.

It's not a microbiological term; it's used according to the standard definition of the word.

Apparently, microbiologist use this term to describe the process of culturing microorganisms from soil. You make a 'slurry' which has both growth media and the soil (which would fall under the english definition of a slurry) and incubate it waiting for growth. Media(Liquid) + soil = Slurry

A slurry can also be used to mean a semi-melted ice water mix. Most people would call it ‘slush’, but I’ve come across it in some protocols before (can’t think of a reference to provide though, so it’ll depend on your particular context).


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Why should you use an annealing temperature about 5°C below the Tm of your primers?
Why should you use an annealing temperature about 5°C below the Tm of your primers?
According to my current research, I think it has something to do with the other reactents in the PCR, but I am not sure.

What's your problem with the answer? Some criticism would help to make it better...

My understanding of this concept was recently corrected by a prof, and your explanation did not seem to get to the point. I will add the answer the prof gave me.

I haven't seen this yet - do you have a literature source for it?

The annealing temperature of a primer is defined as the temperature in which 50% of the nucleotides of the primer are bound to the DNA. 50% annealing proportion will not yield an optimal PCT product. Thus, by lowering the temperature by around 5oC, the proportion of bound primer changes to more then 50% (perhaps around 70 - 80%) thus getting a more precise yield.
This is why we subtract 5oC from the theoretical annealing temperature.

You want to have primers which bind under the conditions of the reaction only to your sequence of interest. If you go too far off the optimal annealing temperature (5°C below the Tm is indeed a relatively good choice in my experience), your will affect the PCR efficency and thus the yield of your reaction.
An annealing temperature, which is much too low allows annealing of your primers to other sites than your intended target with partial annealing or internal base mismatches. This leads to unspecific amplification and lower yields.
If the annealing temperature is too high no primer binding can happen and you will get not PCR product. Alternatively, partial binding can also lead to misprimed products, although this is much less likely than getting no product at all.


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mRNA Sequencing Basepair from Polyadenylation Site?
I was wondering how many basepairs are usually sequenced with mRNA/cDNA illumina methods from upstream of the polyedenlation site?
Thanks.

No one can answer this.  There are too many sequencing methods.

50-75 bp could be achieved.
Refrencing TruSeq® RNA Sample Preparation v2 Guide. My lab used random primers and read lengths were an average of 75 bp in length for an RNA seq project. But controlling distance from polyA wasn't considered in out project.
Using oglio(dT) primers you could try and control a specific length from the polyA tail.Two basic variations use either random primers or oligo(dT) primers for this reaction. Oligo(dT) primers are highly 3’ biased and mostly
suitable for mRNA abundance (expression) analysis. Random primers also result in some bias, which can be reduced by fragmentation of the input RNA.
Source: RNA Sequencing Methods Collection - Illumina, Page 8.
Different lengths can also be achieved for different needs.
Gene expression / RNA Profiling – Quantifying the coding transcriptome typically requires a short single read (often 50–75 bp) to minimize reading across splice junctions while counting all RNAs in the pool.
Transcriptome Analysis – Novel transcriptome assembly and annotation projects tend to benefit from longer, paired-end reads (such as 2 x 75 bp) to enable more complete coverage of the transcripts and identification of novel variants or splice sites. Paired-end reads are required to get information from both 5’ and 3’ ends of RNA species with Stranded RNA-Seq library preparation kits.
Small RNA Analysis – Due to the short length of small RNA, a single read (usually a 50 bp read) usually covers the entire sequence. A read length of 50 bp sequences most small RNAs, plus enough of the adapter to be accurately identified and trimmed during data analysis.
Source: Illumina (Considerations for RNA-Seq read length and coverage)


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Why is ethanol osmotically active if it can enter through the plasma membrane easily?
This has been bugging me for a while, and I can't seem to find an answer to it, and I am sorry if I am asking a lot with this question(s). Firstly, I keep finding sources suggesting that ethanol is osmotically active, but I also know that ethanol can enter the cell readily through passive diffusion, and some sources also say it uses transport proteins - what causes osmotically active behaviour, then?
Secondly, and this is very closely linked to the above, why do cells shrink in the presence of ethanol of high concentrations, if it is able to enter readily, unlike, say, ions? The mechanism seems to be far more complex than I have found regarding simple osmosis for ions and such.
I would like to add that my confusion may also be due to conflicting information I am getting, whether the cell shrinks or grows (or does one then the other), so it is hard for me to even picture if the solution acts as if it is hyper- or hypotonic.
SECOND EDIT: Seems that there is evidence from some sources that suggest ethanol can affect the osmolarity of the solution without itself being "effective", whatever that means. Something to do with the lipid membrane. Again, I keep editing this so people might... possibly... have something to go off when answering this.

I would also add this seems to be a similar case to urea, so answer would likely deal with that case as well.


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What areas of the brain are involved in doing arithmetic operations?
Do neuroscientists already know what areas of the brain are involved in mental calculations? Has any fruitful research been done on that or not yet? Do you think that if we understand what areas of our brain are responsible for doing arithmetical tasks we may one day have the ability to improve someone's calculation skills by non-invasive methods?

neurosynth is a useful tool for answering these kinds of questions.  Go there and enter "arithmetic" in the search bar and you can find a number of studies through meta-analysis and their relevant brain regions on a brain map.  Note it's in beta, so use the "studies" tab to confirm with the literature.


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Why are diabetic people often overweight?
I was looking at diabetes the other day, and I noticed something strange. Lower amounts of lipase are a symptom of diabetes, as is overweightness. However, since lipase is the enzyme that breaks down fats, shouldn't a lack of it mean that less of it enters your blood stream and is simply excreted instead? In that case, how come diabetic people are often overweight?
This question has been bugging me for ages, does anyone know why?

I saw something recently on TV which suggested that being diabetic causes weight problems, rather than previously thought which was being overweight causes diabetes.

How are diabetes and obesity connected in light of low lipase activity?
Short answer: There's more than one type of diabetes.  (And to complicate things, there's also more than one type of lipase.  It's unclear from the question which type were mentioned in what you read.)
Diabetes mellitus is usually divided into Type 1 (insulin-deficient) and Type 2 (insulin-resistant).  Obesity is a risk factor for Type 2 diabetes, but not all diabetics are overweight. In fact, people with Type 1 are often lean.
Decreased lipase activity is not a major symptom of diabetes.  However, these two articles suggest that plasma lipase activity may be lower in cases of Type 1 diabetes but not Type 2.
Junglee, D. et al., Low pancreatic lipase in insulin-dependent diabetics, 1983.
Dendona, P. et al., Exocrine pancreatic function in diabetes mellitus, 1984.

Source : Tortora and Derrickson Principles of anatomy and physiology
I read in the section on diabetes that " The breakdown of stored triglycerides causes weight loss".
 I assume that diabetic people are often overweight not simply because they have diabetes but because they also have many other disorders associated with it.
Please feel free to correct me !

Ok..Did the necessary changes.

People with type 1 Diabetes have a heritable defect in their genes. People with type 2 Diabetes eat too much. The prevalence of type 2 diabetes has increased by a factor of 2 since the 1970's. This means more patients for the endocrinologists and more insulin sales for the pharmaceutical companies.

I think @willam44ism is asking more about the enzymatic mechanism, and this answer doesn't really address his question. Also, are there citations for your argument? It seems likely that the risk factors for type 2 Diabetes are much more complex.


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GO terms for non-model organisms
I have a list of differentially expressed genes from an RNA-Seq experiment in Xenopus laevis that I'm looking to functionally annotate with GO-terms. As X.laevis is not listed in DAVID it seems I have 2 options:

BLAST my DE genes against a database with GO terms (human/mouse) to look for orthologs
Use a program that assigns GO from BLAST results, such as Blast2GO

I've been trying with Blast2GO recently, but find if very slow and generally lacking - does anyone have any experience doing GO in Xenopus or other non-model organisms?

interesting question, but no experience doing this from me. Have you tried BioStars.org?

I've done a functional annotation of a non-model, and used Blast2Go with fine results.
Specifically, I took all of my proteins and queried again the NCBI non redundant (nr) protein database using mpiBLAST, then I analyzed this output using Blast2GO (B2G4PIPE) and a local B2G Database.

Updating this thread to include EnTAP, (Eukaryotic Non-model Transcriptome Annotation Pipeline) which wraps protein domain assignment, orthologous gene family assessment, Gene Ontology term assignment, and KEGG pathway annotation into a single tool. I have used it for annotating sequences from divergent groups of non-model species.
See the paper in Molecular Ecology Resources.

blast2go is on the verge of getting commercialized (as they have started selling PRO versions) and my previous experience was not so good with it.
I used IntrProScan to associate GO terms with the transcripts, it ran long but it reported all the possible sequence features.
To use these custom annotation was tricky for visualization, but thanks to BiNGO, I was able to do it flawlessly. For future use I have documented it here, http://infoplatter.blogspot.in/2014/04/gene-ontology-go-enrichment-analysis-in.html
Good luck!!


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Characterising mechanisms responsible for generating structural variants
I have a high-quality set of structural variant breakpoints from tumour/normal WGS data, and I am interested in digging into the various mechanisms that might be involved in each event.
There are several mechanisms that are proposed to play a role in generating structural variants, including Non-allelic homologous recombination (NAHR), non-homologous end joining (NHEJ/MMEJ), alternative end joining (Alt-EJ) and several replicative mechanisms such as Fork Stalling and Template Switching (FoSTeS/MMBIR).
Each of these are distinct processes, that have occur at different time points in the cell cycle and have different potential for generating genomic rearrangements. However, I have not been able to find a consistent requirement for each mechanism.
I would like to know if anyone can think of a authoritative source for criteria I could use to form a working hypothesis as to the mechanism underlying each variant.
For example, if I have a 10 Kb deletion with 4 bases of microhomolgy at breakpoints I'm currently classifying it as an Alt-EJ event (largely based on the criteria I list below).
Several specific questions:
Microhomology at breakpoints is an essential requirement for several of these mechanisms (FoSTes/MMBIR). However, there appears to be no consensus as to whether this must occur exactly at the breakpoint, or whether it can be several bases away (for example here).
Secondly, according to this paper, the criterial used to classify structural variants is as follows (taken from the MeerKat manual):
NAHR: non-allellic homologous recombination, >100bp homology.
alt-EJ: alternative end joining, 3-100bp homology.
NHEJ: non-homologous end joining, 0-2bp homology or 1-10bp insertion at deletion break point.
FoSTeS: fork stalling and template switching, template switch, >10bp insertion at deletion break points.
However, almost every paper I read suggests different criteria, for example FoSTes events are normal associated with microhomologies at breakpoints rather than insertions.
Can anyone suggest a "consensus" of requirements for each mechanism?


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What obstacle(s) would be most prevalent in an attempt to use virotherapy to inject Cas into cells to target a cancerous mutation?
Let's say a human cell mutates cancerously, we identify the mutated gene sequence and use CRISPR to mutate the patient's cells to include some variation of the cas genes and spacer sequences matching the mutated cancerous sequence.
Then design a virus to "infect" cells (cancerous and healthy) with this cas gene sequence and spacer sequences.
The infected cells would then produce a specific cas9-like protein targeting the mutated cancerous gene sequence in the patient. As the modified protein producing cells multiplied to replace the old ones, the custom cas9-like protein would detect and remove the targeted cancerous sequence.
More elaborately the approach could be used to inject a large library of known cancerous sequences as cas spacers in reproductive cells to start developing a species-wide defense against a significant range of cancerous mutations.
What primary obstacles would be in the way? I suspect research has been done on this.
My knowledge so far:

Basic understanding of virotherapy - I'd like to clarify my question is asking about something beyond research I've seen on anti-cancer oncolytic viruses which target cancer cells. My question is about repairing the cells rather than killing them.
A big picture of how CRISPR functions and how it can be modified to achieve specific gene editing functions. Spacer DNA sequences matching targeted gene sequences (usually threats such as bacteriophages) are used by the cas genes to produce proteins called cas9 (or some variation) which couple with crRNA and tracrRNA to match and slice targeted DNA sequences.
a closer look at the specifics of cas9 and its behavior.

Potential problems I considered but couldn't find specific studies on:

Whether the viral delivery of the modified dna would be prevented by the immune system before all the cancer cells could be "infected".

Whether human DNA's size (roughly 1000x the size of some bacteria DNA) might be too "large of a search space" for the cas9 or cas9-like proteins to "find" the targeted sequence.

Whether customization of cas9 into some more specialized / effective variant would overcome any obstacles to this approach.

I don't have time for a real answer with citations, but briefly - by the time a cell becomes cancerous, it has already suffered at least two major mutations, and in reality tumors have many more. Genome instability is a hallmark of cancer. So, your targeted CRISPR/cas9 may have some effect in, say, repairing a major tumor driver, just like an antibody therapy, eventually the tumor is going to mutate around it and keep growing through some other mechanism.


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Identify this tree from Nepal
This is a picture of a tree in Nepal. Can somebody identify it?

Do you have some more picture of the leafes? Will be hard to identify the tree solely based on the bark

I have uploaded photo of leaf.

The leaves on the top left have different veins than the leaf from the photo, Are they from the same tree?


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If motor neurons are part of the CNS, what is the PNS made of?
It is my understanding that motor neurons transmit messages to the myocytes of skeletal muscles all over the body. This should make them part of the peripheral nervous system that transmits both the voluntary and involuntary movement of muscles. Now, I came across this site that says motor neurons are part of the Central Nervous system. https://qbi.uq.edu.au/brain/brain-anatomy/types-neurons. Which is right? My book specifying the peripheral information, or the website?

Comments are not for extended discussion; this conversation has been moved to chat.

The peripheral nervous system refers to parts of the nervous system outside the brain and spinal cord. It includes the cranial nerves, spinal nerves and their roots and branches, peripheral nerves, and neuromuscular junctions. The anterior horn cells, although technically part of the central nervous system (CNS), are sometimes discussed with the peripheral nervous system because they are part of the motor unit.

It appears that even though the motor neurone body lies inside the CNS, the spinal nerves are by definition part of the PNS.  Clearly some authors don't follow the convention hence the conflicting views.
https://emedicine.medscape.com/article/1948687-overview

I've sent feedback to the University of Queensland to inform them!

Eww a commercial source.

As far as I know universities are run as commercial entities as well.


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Could large plants grow out of large, solid rock in some way? What is primarily stopping them?
Roots of plants are known for being able to pierce through the firm soil and even solid stone to some extent. However, it occurred to me recently that I might be overestimating this ability as soil isn't the continuous material it seems from a large scale, but rather it is made of many small but firm granules connected by softer organic material which got me wondering just how important the granulation of soil is.
Typically, I don't see large stemmed plants growing out of solid rock despite that many granules of soil have a similar hardness to solid rock. But, could a plant that normally grows in soil grow instead in solid rock under the right circumstances? Soil is granulated, whereas solid rock is not.
I'm no expert, so I can only imagine different possible scenarios.
Could a large solid rock support a large and stemmed plant if it was porous enough? In other words, is it unimportant that the rock is very firm so long as there is enough exposed surface area to allow the chemical reactions that take place during the ion exchange at the roots and possibly break down the stone?
Or alternatively, it may not even be the porous or granule nature, but it might simply be the solution water carries. Could an large plant grow off of a large and smoother solid stone alone with roots rested near the base, but, if there was water running fast enough and warm enough to dissolve the surface of the rock and allow the ion exchange to take place in roots once the water was carried downstream to those roots?
Perhaps it's neither of those possibilities and it is solely the ability of a plant to anchor itself that matters the most in this issue. Even if a plant could pierce through the stone with its microscopic roots, since its stem also grows proportionately, if a plant can't anchor itself then it will just be blown away or washed off, so only small plants can anchor themselves to rocks.
Which of these traits is the most important factor in why plants don't typically grow out of larger solid rock, and can it be overcome to successfully grow large stemmed plants out of large solid rock?


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How are ants able to dig with such pointy limbs?
Digging is usually efficient with somewhat broader structures shovels, no one tries to shovel with an ice-pick. Given that ants have very pointy mandibles and thin wispy legs, how are they able to dig anything? Is it  honestly solely by the means that the granules of soil are somehow coincidentally always the right size to fit in their mandibles?

Wow nothing after all this time, I didn't think this would be that hard of a question.

"pointy" is relative term. Try to shovel pieces that are 1m/3ft wide using garden shovel. You look at ant with your eyes, not ant's

It is a relative term, but that doesn't magically make it any less true. Obviously we are talking pointy relative to a human scale, often able to pierce human skin at terrestrial pressures. If we need additional information about the detail of their body at a finer level of observation, that is still relevant information towards answering the question.

what have you done to asnwer this quesiton?

I did research on people who raised ant farms. I was lucky enough to find a video that showed a close up of ants digging in a glass vial and it showed that they were moving artificial granules. However, this is not the same as their natural environment, so I don't actually know of the granules are realistic or if the ants instinctually adapted to the artificial granules. There's plenty of random sites giving vague entries about what ants use digging for, but there is little on the actual mechanics of how they are able to dig in regular dirt in the first place.

Wow, STILL no answer, maybe a research paper can be written about this since the answer is so pervasive. I've had that happen before, I did research on the mechanisms of ants ability to stick and discovered that their saliva contributed to it over smooth surfaces.


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What's the name for this kind of pointy/raised texture in animals?
I was in a store and I saw a jackfruit, seen here https://livenaturallymagazine.com/all-about-jackfruit/ with this sort of...scaly yet round and also pointy texture.
Then, I could have sworn I saw some kind of texture like this on animals, so I tracked down a couple images, like the back of a bearded dragon https://shannonwild.photoshelter.com/image/I0000Wf4WI2Vn.V0 and the pads of an owl
https://i.pinimg.com/originals/a1/94/07/a19407eff53e0fd06c48144c4541e3d8.jpg
What is the name for this semi-spiky texture, and what is the practical use of its topology?

I don't really know, however I have my suspicions. My initial guess would be the following. For the bearded dragon, I'm guessing it aids in defense. Small spikes protect against attackers. For the owl's feet, I would guess that its utility is completely different: friction. Friction helps holding on to the environment.


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Do birds have quadriceps and thighs fused into their hips?
I'm looking at 3D modeling a large bird like an emu or ostrich, but I don't know how the muscles surrounding the femur connect to the hips/back. It seems weird that the entire thigh and quadriceps would be fused into the hip because that would greatly reduce the range of motion of the femur which affects how I animate it, but I can't find any reference that shows it either way.

Is "Ontogenetic scaling patterns and functional anatomy of the pelvic limb musculature in emus (Dromaius novaehollandiae)" not enough?

No it's not....

Have you tried googling avian muscle anatomy.

This is probably WAAAAY to late to be of any use to you but hey...
So the simple answer is:
Kinda.
You were actually correct to intuit that the femora of birds have a limited range of motion, with most of the limb motion being provided from the "knee"-down.
So you shouldn't animate bird legs the same way that you would the legs of other non-bird animals.
That's not to say that the femur doesn't move - it does but not my much (it typically doesn't extend posteriorly beyond the vertical). Much of the thicc thigh musculature is there for support.

Welcome to Biology.SE! Answers are much more likely to receive a favorable response if you include supporting references (primary literature is best) — that allows non-experts to confirm your assertions and learn more. Without that support, your answer is indistinguishable from opinion. This is a good example of how to format references. ——— Please take the [tour] and then consult the help pages for additional advice on [Answer] effectively on this site. Thank you!


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Do B/T cells form from lymphoid tissue or bone marrow?
This website says lymphocytes are produced in bone marrow https://courses.washington.edu/conj/immune/lymphoid.htm
But if that's true, then what cells do lymphoid tissues produce? It could make sense if bone marrow is a lymphoid tissue, but red blood cells are also produced from bone marrow.

This is a good question and I can see where some confusion can arise. Lymphocytes are a class of cells that include both B and T cells among others. They both have the same precursor cell that being a small lymphocyte [1,2]. The small lymphocyte will grow into a large lymphocyte then differentiate into a pro-B-cell or a pro-T-cell [3]. After differentiation the pro-B-cells are "trained" in the bone marrow and the pro-T-cells are "trained" in the thymus [4,5]. The processes of training for both B and T cells are active areas of research and are quite interesting if a bit confusing.
from [6]
"Lymphoid tissue has several different structural organizations related to its particular function in the immune response. The most highly organized lymphoid tissues are in the thymus and lymph nodes, which are well-defined encapsulated organs with easily identifiable architectures. In the spleen (a soft, purplish organ lying high in the abdomen), the lymphoid tissue is a cylinder of loosely organized cells surrounding small arteries. In the bone marrow this tissue is mixed with the blood-forming cells, and no organization is apparent."
It is true that red blood cells are produced in the bone marrow and are somewhat related to lymphocytes. They are cousins to each other in some way [7].
I hope this helped show the differences in the maturation of T and B cells and cleared up some confusion for you. If you would like to know more I would recommend picking up an immunology book. I used this one [8] and quite liked it when I was taking immunology.
[1] https://en.wikipedia.org/wiki/Lymphocyte
[2] https://medical-dictionary.thefreedictionary.com/small+lymphocyte
[3] https://www.researchgate.net/figure/Life-and-death-decisions-during-B-and-T-cell-developmenta-This-panel-is-a_fig2_8014354
[4] https://www2.nau.edu/~fpm/immunology/Exams/Tcelldevelopment-401.html
[5] https://www.researchgate.net/publication/6196234_B-cell_anergy_From_transgenic_models_to_naturally_occurring_anergic_B_cells
[6] https://www.britannica.com/science/lymphoid-tissue
[7] https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0022042/?figure=1
[8]https://www.amazon.com/Basic-Immunology-Functions-Disorders-Immune/dp/032339082X/ref=sr_1_7?ie=UTF8&qid=1524514359&sr=8-7&keywords=immunology

Thank you for your detailed input. But, what is the direct answer? Does lymphoid tissue actually produce any cells? Because I encountered a biology professor who seems to think T and B lymphocytes "form" in lymphoid tissue.

@JohnJoe To clarify T and B cells are "trained" inside of lymphatic tissue but are not generated from the tissue itself.


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Was iron important for the first life on Earth?
Some ions or compounds are thought not to have become involved or important in the metabolism of living organisms until some time after certain mutations took place. For instance, early life is thought to selectively allow calcium ions through its membrane, but eventually also evolved the ability to selectively allow sodium ions, specifically through a mutation that lead to a change in the composition of a channel protein from glutamine to lysine.
Currently, iron is involved in oxidations involving molecular oxygen, such as in cytochromes and clearly holds a key role in modern life, despite that free iron or even ferric compounds are rarely accessible. From my understanding, iron most likely became incorporated into the metabolism of microbes after during/after aerobic organisms had developed, but this does not rule out the possibility that iron was involved earlier on. So, I am wondering if iron was involved in early life, and details on how would be appreciated.

"a mutation in the structure of amino acids to form lysine"? How exactly does a chemical compound mutate? I would stick to your question and avoid unscientific analogies and unprovable remarks about when different amino acids emerged.

@David since most biological compounds used in life are produced through a genetically control process, saying "X mutated" is a common acceptable shorthand for saying "the genes that controls the production of X mutated changing the structure of X".

@John I dont know in what circles is that acceptable, maybe creationists, but if my student wrote something like this on an exam, I would fail him on the spot - and that would be mercy in comparison what my master or phd advisors would do to him. Structure of a chemical compound cannot mutate, period. If you add or remove an atom from the structure of a chemical compound, it becomes a different compound.
Also, the title is misleading. Asking IF iron was important for the first life on earth is not the same thing as asking WHEN did the iron become important.

I am afraid what you write is neither accepted by or acceptable to professional scientists. Nor can a clause evoking a mechanism be shorthand for the simple statement such as “lysine emerged later” — indeed it is a clear violation of Occam’s Razor. It unjustifiably and unnecessarily implies a knowledge of the order of addition of amino acids to the genetic code, the mechanism by which the code expanded, and some sort of ‘purpose’ in relation to ion transport. I have edited your question to make it scientifically acceptable and appropriate to the question.

@david are you not aware cells will modify amino acids, this is how the majority of amino acids are produced after all. Post-translational modification of animo acids is fairly common.

John, I have taken the time to provide a detailed chemical answer to the title of your question (which I did not alter). You might care to direct your attention to that. Do you understand it? Does it seem satisfactory? Have you any comments on it?

I think it's inappropriate for you to make such a large change like that. Life relied on calcium, then selectively included sodium. I wanted to know if the same kind of thing happened with iron and how in order to track the timeline of the incorporation of different elements for microbial evolution, and my original question got me an answer. https://www.ncbi.nlm.nih.gov/pubmed/24517213

The reinsertion of a revised first paragraph is unnecessary, misleading and a poor analogy for your question. First, you are not asking if iron replaced some other metal or system — or if you meant to do so it is not evident in your question. Second you talk about the acquisition of sodium channels from calcium in “early life”, when the paper you refer to talks about the evolution of the channels in eukaryotes. It would be far more pertinent to expend your effort on justifying your assertion of “iron being rarely accessible" — something that my own answer argues was not necessarily true.

I don't think it's misleading at all, I think you're being too technical (if your assertion is even accurate) where it isn't relevant. What I proposed is an example of the kind of phenomena I am referring where life evolved to incorporate another element and in an understandable way, which continued to happen with more elements like molybdenum, copper, iodine and more. The paper talks about life evolving over the scale of billions of years, and Eukaryotes weren't always around, it took a long time for microbes to develop the traits we see today.

If you wish to address comments to individuals other than the person whose contribution you are commenting on you need to add an @joebloggs to alert him to the fact that the comment is addressed to him. All I can say is that it seems to me that your interest isn't in the chemistry or biochemistry of the evolution of iron metabolism, as your question implies, but rather whether it could provide another example of a change of functionality from the change in a single amino acid. A pity, because the question in your title is interesting, but it requires a knowledge of chemistry to address.

It really doesn't require chemistry at this point, it more or less requires a single date or a yes/no with evidence to support it.

Cyanobacteria require iron for photosynthesis and can be found as fossil stromatolites dating back to 3.5 billion years ago.  Stromatolites are layered structures made up of cyanobacteria and sediment.

Source: https://en.wikipedia.org/wiki/Stromatolite
Modern stromatolites can be found at Shark Bay in Australia, Chetumal Bay in Belize, and Laguna Bacalar in the Yucatan Peninsula.
Cyanobacteria are also believed to have evolved into the first microbes to produce oxygen by photosynthesis, which was a catalyst for the Great Oxygenation Event which occurred around 2.45 billion years ago.

So you're saying life nearly started out as cyanobacteria? This would have to be quite a recent development because I've seen multiple sources in the past say cyanobacteria didn't form until around 2.7 BYA.

@John Joe: Sorry, I thought I had provided this source also.  http://www.ucmp.berkeley.edu/bacteria/cyanofr.html

So if that's true, why was it only much later that the atmosphere became oxygenated?

While I largely agree with this answer, I'd point out that as far as I know we have of knowing how similar the metabolism of these ancient organisms was to extant organisms. There's evidence of morphological similarity but morphological similarity does not necessarily imply biochemical similarity.

So if life already had the capacity to harness iron, why didn't life forms release that oxygen earlier?

@JohnJoe This is discussed in the Wikipedia article on the great oxygenation Event: https://en.wikipedia.org/wiki/Great_Oxygenation_Event#Time_lag_theory - it would have been released but was not yet able to build up.

@JohnJoe if you need to ask a separate question I'd post it as such, not add it in the comments; the answer above fully answers what you actually asked in the body of your question (although your title and question body include different questions).

I guess it all makes sense then. I was just surprised that more developed bacteria appeared that early on contrary to what I thought other sources had suggested, but thank you for sharing.

Summary
It has been proposed that iron was indeed important for the first life on earth, specifically in combination with sulphur. This is because conditions are thought to have existed in volcanic hydrothermal vents that would have allowed formation of iron–sulphur complexes which perform oxido-reduction reactions in modern proteins (as well as more sophisticated functions). Some system for oxido-reduction of chemical compounds is required for life to develop, and the inorganic simplicity of Fe–S clusters, together with their ability to interact with the backbone of proteins, argues for their early involvement, rather than the chemically more elaborate NAD and FAD.
The Archaean Environment
One theory suggests that life  originated volcanic hydrothermal conditions in which the oxidation of iron minerals by hydrogen sulphide would have been possible. It has even been suggested that life originated on the surface of iron sulphides (the ‘Iron–sulphur world hypothesis’), although this answer is more modest in its scope.
Iron–Sulphur Metalloclusters
Modern proteins contain a range of iron-sulphur clusters of varying complexity, but it has been argued in a review in Science by Rees and Howard that the simplest of these — the 2Fe:2S cluster in, e.g. ferredoxin — could have evolved in the conditions mentioned above.

[Different FeS clusters. Note that the external yellow sulphur atoms are from cysteine side-chains of the protein. (Adapted from a review by Johnson et al. (2005))]
Interaction of Iron–Sulphur Clusters with Proteins
In some iron-containing proteins, like cytochrome c, the iron is held in place by a sophisticated organic molecule (haem) and interacts with amino acid side-chains. However in simple iron–sulphur clusters interaction with the NH groups of the protein backbone (in special conformations — ‘nests’ and ‘crowns’) can occur. Thus initially they could have been acquired by simpler proteins, which some believe to have preceded the development of those with the side-chains to provide more sophisticated interaction.

[Interaction of FeS clusters with protein backbone NH groups (blue): A. ‘nest’, B. ‘crown’ with the N atoms in space-filling mode.]
Other Contemporary Redox Cofactors
The intellectual appeal of Fe–S cofactors as being evolutionarily most ancient can be seen if one compares them with the structures of other contemporary redox cofactors (images taken from Berg et al.):

It has been argued that the adenine and ribose moieties of these cofactors attest to an ancient origin — in the supposed RNA world — an idea that I, personally, find appealing. Nevertheless, their emergence would require a mechanism for the synthesis of their functional organic components — nicotinamide and flavin, respectively. In contrast, Fe–S clusters come ‘ready made’.
More Complex Iron–Sulphur Clusters
Iron sulphur clusters are also found in the nitrogenase protein, which converts nitrogen gas to ammonia. This must be a very ancient protein, but its greater complexity (the cluster includes molybdenum) suggests it may have arisen later. Another elaboration is proteins, such as aconitase, that have Fe–S clusters linked by more complex organic groups.

[Iron-containing proteins of greater complexity. Haem, the non-sulphur iron prosthetic group of cytochromes etc. is also shown. Adapted from Berg et al.]
Iron in Photosynthesis
As mentioned by @Kurt, iron is a component of photosystem II in contemporary cyanobacteria. However photosystem II is extremely complex and the precise chemical basis of the non-haem iron requirement is currently unclear. Although perhaps necessary if cyanobacterial photosynthesis were responsible for the great oxygenation, this complexity would suggest a relatively late emergence in the pre-aerobic era.

I have expanded my answer, which is now essentially complete, unless anyone requires details of the metabolic pathways aluded to, which I will be happy to provide.

I think if this was hybridized with the first answer it would have made both better, because the first answer showed that the same premise of cellular respiration took place much earlier than thought with direct physical evidence which explains iron and its role but without much theory, whereas you mainly rely on a conjecture of a specific compound and not direct evidence so much. They "can" interact with background proteins, but did that actually make them necessary? Was there actually a mutation back then that lead microbes to incorporate a modern organelle or metabolite from that compound?

Any statement about metabolism in early evolution depends on deduction rather than physical evidence. The argument of @Kurt could be restated as: contemporary cyanobacteria require iron (for PSII); they are thought to have caused the great oxygenation; hence iron must have been used in metabolism before aerobic life. The argument assumes that photosynthesis in ancient cyanobacteria was the same as today. His photo is only evidence for the existence of cyanobacteria even earlier, but if they had the current PSII they would still be far more elaborate than anything in “the first life on earth”.

Like I said if there was a way to combine both answers I would be open to it, but it's not mere speculation if we can actually see the imprints of the structure of microorganisms. It does assume the same photosynthesis, but it assumes that because there is consistent material evidence for it, whereas your argument is "well, this compound could have been involved because it could have interacted..." and that's why it's called a "hypothesis."


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How does use an action potential from innervation selectively modify tropomyosin over time?
Within a myofibril, the myofilaments move past one another to product muscle contraction if and only if the actin binding sites are exposed to the myosin by locally removing the tropomyosin by binding it with calcium ions
What isn't quite clear to me however is: what does a pulse from a motor neuron do to the tropomyosin in order to to excite this initial change to move the tropomyosin away and expose the actin?
Then, how does the muscle cell and/or motor neuron sustain this state of contraction, and then finally decide to end this state of contraction and return the muscle cell to its relaxed state?
Also, where exactly is the tropomyosin going after it binds with calcium ions?

At the neuromuscular junction, motor neurons release acetylcholine which binds to nicotinic acetylcholine receptors on the muscle. These receptors are ligand-gated ion channels that are permeable to small cations.
Opening these channels depolarizes the muscle cell membrane, which causes the opening of calcium channels, primarily on the sarcoplasmic reticulum (SR) for skeletal muscle. The key channel is called the ryanodine receptor and is either mechanically coupled to a voltage-gated calcium channel (skeletal muscle) or activated by calcium released from voltage-gated calcium channels (smooth & cardiac muscle), but in both cases the change in voltage is the initial signal.
Calcium concentrations are very low in the muscle cell at rest, but high within the sarcoplasmic reticulum so calcium rushes through and some of it binds with troponin (not tropomyosin itself, but they are associated/attached with one another), which releases the hold of tropomyosin on the actin filament.
The calcium-bound tropomyosin doesn't go anywhere, but as calcium is quickly pumped into the SR or buffered up by calcium-binding proteins, troponin is no longer bound to calcium, allowing tropomyosin to block the myosin binding sites.
The increase in calcium concentration is transient, and travels in a wave down the muscle. If there are no further action potentials, the muscle will relax. Constant contraction requires a constant train of action potentials, and the overall strength of the contraction can be regulated by the firing rate of the motor neuron.
The Wikipedia pages for muscle contraction, tropomyosin, voltage-gated calcium channel, and ryanodine receptor can all be helpful. I'd also recommend a basic textbook on neuroscience, which typically covers neuron effects on muscles and some of the mechanics of muscle contraction. I typically recommend Purves, see https://neuroscience5e.sinauer.com/ or a library or anyplace you get books from (any edition is fine).


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Which filament slides past which?
Somehow I haven't found anyone on the internet can answer this: during muscle contraction, does the thin myofilament slide past the stationary thick myofilament, or does the thick myofilament slide past the stationary thin myofilament?

think of it this way : the thin filaments are attached to the Z-line(with the help of Z -disc) and thick filaments with the help of a spring like protein(titin). Now, when contraction occurs, myosin head pulls the actin filament towards it (power stroke) : i.e. Z-line is pulled towards the centre and the length of sarcomere shortens. So, actin is pulled towards the centre : Thin filament slide over the thick ones. PS: I'll try to add a detailed ans later on. =)

This is an article on muscle contraction. It'll help to solve your problems. Especially read the part where the information about mechanism of power stroke is given (above figure 11.24).
Ask if you have furthur questions after reading this article!
https://www.ncbi.nlm.nih.gov/books/NBK9961/

thick filaments slide over thin as cross bridges are formed by thin filament which slides thick filament and sandwich like structure is formed and Z-line disappears

Thank you for answering. Do you have any credible references however?

actually i read abou that in my state board textbook of biology

can you reference the textbook then?

i already reffered it and wrote answer

That's not a reference, what is the title of the book? Who is the author or publisher? What year was it published?


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Why doesn't surgical steel cause inflammation?
It seems some very specific alloys like implant surgical steel and titanium don't cause inflammation in the human body, but when I asked my doctor about it, they simply said "it just has some chemical property that doesn't cause it."
So...what exactly is special about these metals compositions as to not cause inflammation like most other things would?

Surgical steel can cause some inflammation (basically everything can) -
it's just far less inflammatory than other metals and many other materials. You may want to edit your question to avoid an attack from the pedants. I'd also suggest removing the x-files references, they're mostly just distracting and not important for your actual question if you want it to be about biology and not science fiction.

Usually people irrationally complain if there's no context or apparent reason for a question.

Some can
First the terms you are looking for is biocompatibility and bioactivity. The study of them is called biomaterial science. Both fields are relatively new so complete answers do not exist, there has been a certain amount of trial and error in find suitable materials.
There are a dozen factors that go into these things, toxicity, whether they corrode in the body, whether they are soluble, chemical reactivity, whether they trigger an immune response, whether they can bond with bone or other tissues, mechanical resilience, steric and electrical properties, wetting, even how smooth it can be made can have an effect. The other important thing is many materials have very different biocompatibility depending how and where they are used, different parts of the body can have very different conditions, for instance material used in a bone screw might be useless in a dental implant (different PH and chemical exposure) or a heart valve (different mechanical and electrical requirements).
Titanium has remarkable biocompatibility with internal bone implant, its already low reactivity actually gets better as its surface oxidizes as it becomes slightly polarized and will incorporate many cellular surface molecules(passivation). Many of the factors that make titanium useful in this way are still being studied.
Surgical steel is a broad term that covers several types of steel used for  multiple medicalpurposes, it includes steel implant and steel only used for instruments. Some forms of surgical steel work great for instruments but are rarely for internal implants, often because the same nickel content that makes them corrosion resistant is also bioreactive, triggering an immune response, but its superior mechanical properties means it still is sometimes used as implants, especially temporary implants were corrosion is less of an issue.  (paper, sorry it is only available in German). Nickel free surgical steels used in cutting implements is stronger and harder (what you want in a medical blade) but  without nickel it will quickly corrode in the body.
Part of the reason your doctor did not know was some aspects are still unknown in general and the study of these properties is rather specialized so a general practitioner may have never studied the parts that are known. Consider an  pilot still know very little detailed metallurgy of their engine components, and still be an excellent pilot becasue they don't really need to know.  Heck most of reason I know anything about it is I used to hang out with a guy who made titanium implant screws for a living and it just sounded kinda interesting so I read up on it.

Coincidence ? Vitallium has been used in gas turbines since the 30's ( the first engines, and it still has a place in these engines.)

As far as I know "surgical steel" for cutting tools is never used for implants . And, reactions to metals are mostly allergys. Surgical steels are martensitic ( hard) chrome stainless , eg 440 A, B, C, and 420. Some surgical tools are 316 stainless which is also used for implants. Better implants are made of titanium usually with a titanium oxide surface ; bone will attach to the oxide surface but generally not to 316 SS. There is Ni in 316 stainless and some people are allergic to Ni. Anything with Cu would be a terrible choice as it has strong toxic properties; eg , it is used to clad ships to prevent barnacles . There are some other minor use of ,eg. Vitallium ( alloy of chrome and cobalt) and others.

After looking at Johns' reference above, I see Vitallium ( aka. Stellite 21, aka cobalt/chrome) is becoming more common again .It is likely replacing some 316 SS because of nickel allergies. And is cheaper than Ti after you put on the plasma spray oxide . Ti is still the better choice , good bone bonding, lower density , lower stiffness - more like bone.

Surgical steel doesn't cause inflammation because (i) it has very little solubility, and (ii) what little iron ions do get dissolved into bodily fluids are chemically too simple to be recognized by the immune system and trigger an immune response. Moreover, the human body naturally contains small amounts of iron, e.g. bound to myoglobin in cardiac and muscle tissue.

I would think a practicing graduate physician for 20+ years would know an answer like that off the top of their head, are you sure it's that simple? Copper metal itself is insoluble, and copper is also found in the human body, and copper metal has an extremely simple chemical formula Cu, and yet something tells me a copper implant is still going to cause inflammation if insert it into someone. Could it possibly be more related to the ligands it forms?

Copper and iron have slightly different physical and chemical properties, but basically that's it. Steel is used because additives like silicon or carbon permit fine tuning of different physical properties like tensile strength and expansion coefficient + it's cheap and abundant. Most things you can achieve with steel you can achieve with titanium as well, but titanium is a lot more expensive, so you use it only when you really need to.

But see what are those "slight differences" that define whether something causes inflammation or not?

Inflammation may be caused by complex macromolecules such as proteins and nucleic acids, which are recognized by the immune system or (a lot more rarely) simple molecules, which become bound to larger molecules, like proteins. In the latter case, the immune system is able to recognize the small molecule-protein complex, which initiates inflammation; such a potentially inflammatory molecule is called a hapten. Copper may be slightly more prone to binding/adsorbing to proteins because of factors such as electronic structure, the solubility of the specific material/alloy, and others.


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How are bioremediation microbes removed from the environment once they perform their function?
In the case of bioaugmentation, microbes are introduced into the environment to clean up and absorb a certain pollutant. My question is how is that microbe then removed from the environment once it performs its function?

A bit broad.  Sometimes it will die off when food supply is too small to support the population; sometimes it will need to be removed with poisons or predators; sometimes it doesn't need to be removed as it is relatively benign to the environment.  What case of bioaugmentation are you referring to specifically?

Heavy metal bioaugmentation.

Usually you have to introduce conditions which hinder multiplication of the microbe such as altering the pH and emperature. This is hard to achieve in a large environment, alternatively, you can introduce a recombinant of that microbe which posses a survivability threat to the initial microbe.

Could you add some sources describing these steps actually being performed?


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Can you Interrupt a promoter region by inserting another promoter region into it?
I currently have a plasmid (pFPV25.1) which contains a promoter region with multiple cloning sights in it. I would like to place a new promoter I have isolated, and I was wondering whether I could  insert the new promoter into the middle of the old promoter; would that result in the new promoter controlling the gene of interest?
What I understand is that the RNA sequence that would be transcribed will change, but the start codon for translation would be kept consistent by doing this method, resulting in the gene being controlled by the new promoter.
Thanks.

If you're trying to study the new promoter, you should probably remove the old one completely. There should be restriction sites outside of the MCS that you could use to cut the old one out and insert the new one.

If you do choose to insert the new one inside of the old one, you should find a way to convince yourself (and the reviewers) that the old one has in fact been inactivated by the insertion.

Ok, I will sequence the plasmid would this be enough? What protocol would you recommend.

I'm not saying that you need to confirm that the insertion has taken place but rather confirm that the insertion completely abrogates activity of the old promoter. I'm entirely unfamiliar with the plasmid and promoter that you are using, so it may be that this has already been done and reported in literature. However, if this is something new you are trying, you need to show that expression is controlled entirely by the new promoter and not some residual activity of the old promoter, or at least rationalize that that is the case based on the nature of the old promoter and the insertion site.

The new promoter that I am using should only be activated in the presence of a heavy metal. The other one is activated all the time. Thus, once I do insert into the plasmid, and no GFP is seen to be produced  then this confirms that the previous promoter have been destroyed.

of course, not in the presence of a heavy metal

That would be quite convincing. However, can you be sure that elements of the old promoter don't interact with the new promoter? Again, I don't know anything about the promoter and so this may not be an issue. I'm just trying to think of potential problems.

agreed. Its not the best idea


text:
Why is CLL B-Cell leukemia t(12;21) more responsive to chemotherapy?
Chronic Lympoid Leukemia targeting B-Cell (with the particular translocation mutation on chromosome 12 and 21) is known to be more responsive to chemotherapy. Is there a known molecular mechanism for why?


text:
What Does Transcription Factor E25 Activate When a Cell is Transitioning from G1 to S
Cyclin D/ CDK4 phosphorylates Rb allowing for the activation of transcription factor E25 during the G1 phase of the cell cycle. Supposedly, this transcription factor then activates as set of genes helping the cell to enter the S phase.
My question is what genes do E25 exactly activate? Are there any associated pathways with these genes involved in transitioning the cell from G1 to S?


text:
Reasoning for Stomatal Distribution Between Monocot and Dicot
When you compare the stomatal arrangement of bean and corn plants under a microscope, you notice that the corn's stomata arrangement is much more organized and linear then the beans. I am wondering whether there is an evolutionary explanation for why that developed?
One thing to note is that the morphologies of the epithelial tissue cells are very different, so maybe it is a natural consequence of that?

Wouldn't this be a natural result of the differences in veining in the leaves?  The parallel veins in the corn leaf would constrain the placement of the stomata to the rather linear area between the veins.

Sounds plausible, can you provide some reference?


text:
Full Sequence for Plasmid pMG101
I am trying to find the full plasmid sequence for pMG101. I have been looking through other papers that have sequenced this plasmid. The GenBank access numbers I got are the following: AY009372–AY009396, ASRI00000000. However, when I go on genbank it gives me a result saying it is not there..... I am stuck and not sure how I am suppose to find this full plasmid sequence. Does anyone know another way to find it?

Here it is: http://www.ncbi.nlm.nih.gov/nuccore/4206623?report=graph
This is the same plasmid as in E. Coli J53. This is the newest sequence.

Looks as if you'll have to do some reconstruction work building the full sequence from the information here and elsewhere in this paper:

Nucleotide sequence accession numbers.The DDBJ/EMBL/GenBank accession numbers for the sequences reported in this paper are AB031076(the SalI-XhoI 3.0-kb fragment of pMG101), D84187(rDNA for strain S55), D86354 (rDNA for USDA 4362), D86355 (rDNA for USDA 4377), AB031077 (plasmid pMG103), and AB031078 (plasmid pMG105).

--Sequence Analysis of the Cryptic Plasmid pMG101 from Rhodopseudomonas palustris and Construction of Stable Cloning Vectors

See I do not need the whole sequence, I just need the SilR SilS and SilE, but not as an individual protein, but all together. Also what do you mean my reconstruction work, like I need to sequence it again, or need to start putting the plasmid together based off of already sequenced parts?

Just from a quick skim of the paper, it seems like the information you need is all there, you just have to piece it together.

So I found this: http://www.ncbi.nlm.nih.gov/nuccore/AF067954.1. This is the part of the plasmid I am looking for, however, this plasmid pMG101 was not isolated from the same bacterial strain that I am using. I am going to be doing primer design, does this matter?

We have no way of telling.  Primers are cheap; if you have good controls downstream, consider making the primers and seeing if they work.

I just found out it is the same sequence. E. Coli J53's plasmid was derived from this bacterial plasmid.


text:
How do proteins 'know' where to go?
I've just found once again this famous animation I've been curious about for many years:
https://youtu.be/WFCvkkDSfIU?t=213
Here's a screenshot from the animation:

The green blobs (proteins, I believe) are moving from outside the scene to "the crowded area" (where unzipping happens). Then some of them (paler-green ones) are leaving in the same way as they came.
I am curious about how they are doing it!
I suspect that the "crowded area" emits some molecules (or perhaps ions), and "green blobs" might be literally electromagnetically attracted to the source due to density gradient of those ions. As for the "paler ones", they might be gaining on some other molecules (after contact), which probably disables their attraction to the "gradient". And the reason why they're so "determined" while leaving remains unclear, but I can guess that the same "gradient" molecules might be just pushing on them (as far as shown).
I would like to watch or read more about such details! And also about two-legged proteins from the end of that video — the ones that look like giant fighting robots from the Star Wars 1st trilogy.
Surely, these couple of things alone would take at least few month of studying.

As a fun bonus, that's somewhat close to the true speed of the process (about 50 base pairs per second).

Even though this animation is very well-known and the narrator says it is "... an accurate representation of the actual DNA replication machine ...", be very careful of its visual appeal. It is, after all, only a fancy animation for educational purposes. Some aspects of the process are shown correctly, but many are simplified, omitted or prettified, and can thus be misleading.
For example, a key ingredient not being shown in this animation (for obvious reasons) is water. DNA and the accompanying proteins do not float in free space, they are immersed in water. But not only that – intracellular molecular enivornments are far more crowded with other proteins than shown in the animation. See for example this whole-cell 3D model of a Mycoplasma bacterium.
Molecules don't know where to go. They move randomly1, bump into other molecules, and generally tend to disperse evenly across the solution. If you put a little drop of food color in a glass of water, it will eventually spread throughout the water. The same "force" drives macromolecules (such as enzymes shown in the animation) to move around. But when two molecules which are somehow "compatible" just happen to by chance come very very (!) close to each other2, molecular forces can help them position in the right way and stick them together. You can watch a simulation3 of molecular dynamics showing a small molecule finding its way into a large protein.
Although your hypothesis about some (mysterious) ions signalization and electromagnetic attraction is somehow reasonable, this is not the correct explanation for the process in animation4. First, electric forces in solution with ions are weak and short-ranged due to screening. Second, they could not be specific enough to attract only some molecules and not the others.
I put some keywords such as Brownian motion, diffusion, macromolecular crowding, molecular dynamics ... with links in my text which you can use to start exploring the topic of physical biology. Any textbook on cell biology or physical biology will be a good start, but the choice very much depends on your prior knowledge.
Oh, and the two-legged proteins are molecular motor proteins.

1 There is also a directed transport of substances inside of a cell, but this is a different phenomenon.
2 Macromolecular crowding actually hinders the movement (diffusion) of molecules around the solution (smaller diffusion coefficient), but it helps them stick together (larger binding constant).
3 Mondal et al. (2018)
4 Moving along a gradient of some chemical does happen, but it usually involves membranes or it happens at larger scales.

The motor protein animation is also misleading. He just gave everything a simple repeating walk cycle when in reality it's far more irregular. As far as I can tell he made these animations solo, they're not peer reviewed, and I can find no evidence he's ever done research in this area, so I wouldn't presume any aspect of the animations to be accurate.

This answer is specific to the "two-legged" proteins from the end of the video (motor proteins).
The animation shows identical proteins moving in perfect lockstep, but really there is wide variance in the time between steps, as seen in this graph of the motion of kinesin from M. J. Schnitzer and S. M. Block, Kinesin hydrolyses one ATP per 8-nm step, doi:10.1038/41111:

Here's a plot of the motion of myosin V from a different paper, showing a similar pattern.
This video shows what I think is a somewhat more accurate picture of the motion of kinesin, though it still shows all steps as taking a similar time.
The animations in the question were created by Drew Berry, who is also the presenter. My impression from his voiceover ("It's that mechanical. It's molecular clockwork. [...] This is all derived accurately from the science.") is that he didn't know that his depiction was inaccurate, though that was certainly known in the field at that time (the papers I linked were published years earlier). He doesn't seem to have ever done any biological research, and is primarily an artist. As such I would be suspicious of the accuracy of everything in his videos, but I'm not qualified to evaluate them.

There have been some suggestions that biological molecules may 'know where to go'.
Barry Honig's group at Columbia analyzed the electrical charge arrangements in protein and proposed that by placing charges throughout the protein in specific configurations that electrical fields could be focused and direct diffusion to accelerate the function of some proteins esp in finding their binding partners and reaction substrates.
An early paper for their electrical field analysis package DelPhi proposed that Super Oxide Dismutase had a strong electrical field that would strongly attract the negatively charged superoxide ion into its binding pocket.  In particular the hydrophobic core's electrical permittivity in contrast to the water around the protein has a pronounced effect on the electrical field around the protein.
This is still not common analysis because such models are often compromised compared to the realities at atomic scales but they are probably qualitatively valid.  Honig's work was most likely motivated by the regular measurements that diffusion in biology is faster than it has a right to be.  In particular Super Oxide Dismutase's reaction constant is orders of magnitude above diffusion.
I am looking for the original work above and will bring it in.  Another more relevant case to the question is that DNA binding proteins also [find their binding sites faster than diffusion would allow]3.  DNA is highly negatively charged (albeit with positively charged ions surrounding it in solution) certainly its reasonable to believe that the orientation of the protein to its intended binding must be important and that the cylindrical shape of the field around the DNA would explain some of these observations. Certainly the advantage of such an adaptation in the protein would be highly preferred in an evolutionary environment.
This topic is covered in the case of several molecules in this reference.  Here i've scraped a figure from the paper showing the positive charges around
PartII
I just got to attend a short conference and i have another interesting take on this.
The current thinking is that the ribosome and RNA polymerase both have a bubble of proteins that condense around them that are specifically involved in translation or transcription respectively.  These 'condensates' are not compartments in the cell but self assemble because of protein protein interactions.  This would make the functions in the cell partitioned because of protein self- assembly.  Evidence is still coming together but another example of how biology does not submit to Occam's Razor very well.
Reference : "Honig and Nicholls, "Classical Electrostatics in Biology and Chemistry" Science v268 p1114 (1995)

I'm not as familiar with the intricacies of e.g. protein synthesis, but for, say, vesicle release at synapses between neurons I feel like saying biology "knows where to go" is a bit magical; what actually happens is quite simple and intuitive: the various proteins involved are co-localized via associations with other structural proteins, which means that when, say, calcium ions enter through an ion channel, they aren't diffusing throughout the volume of the cell, they're diffusing a very short distance to a calcium sensor located right next to the channel.

sure - though that is a specific system among the many in the cell.  there are some cases like clathrate mediate endocytosis and the endoplasmic reticulum and mitochondria that are better studied than others. the question is pretty broad and perhaps focused on individual proteins specifically. would love to see a good question on synaptic vesicles.  there are visualizations of these processes available too which are pretty specific.


text:
Are all animals “information seeking”?
I read on Britannica that all animals down to microorganisms are "information seeking", but there was no source to back up the claim.

One way to begin exploring curiosity is to understand ‘information seeking’. This behavior is observable across the entire animal kingdom – from apes and dolphins all the way down to crabs and tiny nematode worms. ‘Information seeking’ means that every animal seeks information about their environment. This is so they know how to navigate it. In fact, it’s why sensory organs exist – to supply the brain with information that helps you understand your environment and make better choices.

Are there any sources or facts to support these claims?

What are you doing right now? (Information seeking.) All animals, even the smallest "micro"organisms, at a minimum seek conditions conducive to life. That requires information seeking.

This might be a better question for the Philosophy stack.

The answer is going to entirely depend on how you define "information seeking". How do you choose to define it?

@BryanKrause. Britannica says “every animal seeks information about their environment”

@anongoodnurse Where is your evidence?

Try slime-molds - an article regarding how they sense their environment and respond to it. It's a general assumption of any organism that moves or can act in any way, it's been observed and studied at all levels of size and complexity. In a world where it's eat or be eaten, it's more likely to lead to a successful life passing on genes to offspring if you can tell your food from a predator.

As @BryanKrause stated, how you define "information seeking" matters. If you define it as intellectual curiosity, the claim is preposterous. If you define it as movement towards conditions necessary for life, then the claim is true. The burden of proof is not mine in a comment. Have you done any searches in an attempt to answer the question? Please show us, as it's strongly recommended on this site (see the [tour]). And define your terms. Thanks.

@Aruralreader - I doubt the the OP is asking about knowledge, truth, ethics, or the meaning of life. I might be entirely wrong, though.

@anongoodnurse I updated the post with edits someone recommended, and the original source and definition are there. Also, how would say a jellyfish be information seeking?

For jellyfish, see rhopalium. But you really should try to look these things up for yourself before asking, it's a requirement here to show your research when posting, and comments aren't for the purpose of answering supplementary questions or starting discussions, just for offering guidance to new users  as to how to use the site and suggesting improvements to the original post.

The answer is going to entirely depend on how you define "information seeking". How do you choose to define it? If Britannica does not define what they mean by "information seeking" then that statement is not useful by itself. It's common to encounter these sorts of statements in writing targeted to a non-specialist audience. They are not meant to be taken quite so literally, they're designed to get your mind working and exploring to help you interpret the next things they're going to say. So, let's look at what else they say:

This is so they know how to navigate it.

Not all animals even move, so for this to make sense for "all animals" it must be a pretty broad meaning of "navigate" to be true.

In fact, it’s why sensory organs exist – to supply the brain with information that helps you understand your environment and make better choices.

Every animal has some ability to sense the outside world; I'd argue that even every plant and single-celled organism does as well, this is an absolute requirement for life.

to supply the brain with information

Well, we're back to more specific then, many animal species do not have brains. Sponges, for one; cnidarians also, though they do have a nervous system they're not typically thought of as having a brain.
So, it seems that all Britannica means by "information seeking" is "somehow collect information from the outside world". That's not a very strong statement since "collecting information" can mean almost anything. But, it's also not the sort of thing anyone can prove: there could always be some hypothetical life out there that doesn't collect information but it's not anything we've found.

I thought that mobility at some life stage was one of the primary characteristics of the animal kingdom, and that they must be eukaryotes. Many bacteria are non-motile, and they are prokaryotes. However, bacteria do reproduce under the right conditions, but does this involve "information"? Is it possible to react without "information"? Yeast doesn't move towards sugars. It does metabolize (react) sugar, though.

@anongoodnurse Only as juveniles/gametes. The source quote specified animals but bacteria certainly process information about the outside world, even as simple as regulating enzymatic pathways in response to different food sources. My point is really that one can bicker indefinitely about what "counts" or not but it doesn't really provide any additional knowledge or understanding to do so.

The world “seek” is the problem in my book. For me it implies conscious volition, which would differentiate it from merely *receiving” signals from the environment. The poster could do worse than investigate the history of the usage of the word, perhaps by inflicting himself on SE English Language and Usage.

@David Yes, though a closer read of the original source does not make it seem that "conscious volition" is part of the claim being made; I'd consider the use of the word "seek" to be anthropomorphizing that is not really necessary.

@anongoodnurse Part of the problem is that "animals" is a pretty vague definition to begin with. In any case, I agree with this answer in that "information seeking" is a useless classification even if exists, especially in light of the fact seeing as how many other things also "take in, information".

@David - The entry does discuss curiosity, but the quote the OP refers to is sensory info: "‘Information seeking’ means that every animal seeks information about their environment. This is so they know how to navigate it. In fact, it’s why sensory organs exist – to supply the brain with information that helps you understand your environment and make better choices." Although then "choices" becomes a problem...

@DKNguyen - It's not that vague. Nine reasonably reliable sites out of 10 will define it exactly the same way.

@anongoodnurse I've never heard of motility as a requirement, and it seems a rather arbitrary one at that when some things border so close to being immobile.

@DKNguyen - I haven't read one yet that didn't mention motility, even so far as making the case for corals (stationary) as animals. Sponges, though, have been described as "sluggish". Heh. But they do have a motile larval form.

@BryanKrause so all animals have the ability to sense the outside world and respond according to their biological composition is a certain fact

@HasanZaeem To the extent that I can't comprehend any possible counterexample, yes, but what is it that you can do with that information? It doesn't seem very useful to me. Better to understand how organisms function specifically rather than aiming for such generalities. Biology isn't physics.

@anongoodnurse — Yes, the question is very much one of semantics, which  is why I don't think the question admits a biological answer. However in a philosophical answer I would say that if one classes a simple bacterial response to environment as "seeking information" then the same is true for the response of a plant to light or gravity. Would one really be prepared to say that plants seek information?


text:
Water potential problem
$$
\begin{align*}
\text{Left cell} \qquad& \text{Right cell} \\
\Psi_w=\pu{-1400 kPa} \qquad& \Psi_w=\pu{-600kPa} \\
\Psi_p=\pu{600 kPa} \qquad& \Psi_p=\pu{800kPa} \\
\Psi_s=\pu{-2000 kPa} \qquad& \Psi_s=\pu{-1400kPa} \\
\end{align*}
$$
This is the data given, and we have to find the water potential, solute potential and pressure potential at equilibrium. I can't seem to find any website or video for solving these types of questions.
I tried and got the answer equilibrium water potential to be about -1000 kPa, but it seems there can be multiple answers of solute and pressure potential.
So my questions are:
In this problem, are there multiple answers for solute and pressure potential, and is my water potential answer correct?

How is this a question about biology?

It is in my biology textbook. And I think it's part of A level biology course as well.

Biology is the study of life. Your question makes no reference to any living organism. It also presents the problem as a graphic which is not permissible as it cannot be indexed and discriminates against those with visual deficiencies. Please take the trouble to write out your question properly making the biological context clear, and explaining how you arived at your answer. If the question is in a text book (please name it) then one would expect it to include the necessary information for solving the problem. What did you find there?