using histological techniques, and test the conditions for the survivability of DNA. They will then attempt to isolate a DNA sample using the technique described below, and conduct a PCR amplification of the DNA to increase the amount of DNA available for testing. This amplified DNA is then sequenced. Care is taken to verify that the sequence matches the phylogenetic traits of the organism. When an organism dies, a technique called amino acid dating can be used to age the organism. It inspects the degree of racemization of aspartic acid, leucine, and alanine within the tissue. As time passes, the D/L ratio (where "D" and "L" are mirror images of each other) increase from 0 to 1. In samples where the D/L ratio of aspartic acid is greater than 0.08, ancient DNA sequences can not be retrieved (as of 1996). Mitochondrial DNA vs. nuclear DNA Mitochondrial DNA (mtDNA) is separate from one's nuclear DNA. It is present in organelles called mitochondria in each cell. Unlike nuclear DNA, which is inherited from both parents and rearranged every generation, an exact copy of mitochondrial DNA gets passed down from mother to her sons and daughters. The benefits of performing DNA analysis with Mitochondrial DNA is that it has a far smaller mutation rate than nuclear DNA, making tracking lineages on the scale of tens of thousands of years much easier. Knowing the base mutation rate for mtDNA, (in humans this rate is also known as the Human mitochondrial molecular clock) one can determine the amount of time any two lineages have been separated. Another advantage of mtDNA is that thousands of copies of it exist in every cell, whereas only two copies of nuclear DNA exist in each cell. All eukaryotes, a group which includes all plants, animals, and fungi, have mtDNA. A disadvantage of mtDNA is that only the maternal line is represented. For example, a child will inherit 1/8 of its DNA from each of its eight great-grandparents, however it will inherit an exact clone of its maternal great-grandmother's mtDNA. This is analogous to a child inheriting only his paternal great-grandfather's last name, and not a mix of all of the eight surnames. Isolation There are many things to consider when isolating a substance. First, depending upon what it is and where it is located, there are protocols that must be carried out in order to avoid contamination and further