Do I not have any alleles from my mom's mom & my dad's dad?
Speaking of your DNA in general, you have alleles from all four of your grandparents.  The 22 pairs of autosomes (non-sex chromosomes) can receive DNA from all four with random mixing.  On a few chromosome pairs you may be missing alleles from one of your grandparents due to the randomness, but on average you will have about a quarter of your autosomes from each of them.
The X (and Y, for males) chromosomes are special, though.  The X you inherit from your mother will have alleles from both your maternal grandparents.  The X that you, as a female, get from your father has no alleles from his father, so that grandfather's X alleles are always missing from your genome.
Because of the random mixing, you will have slightly varying amounts of DNA from each of your grandparents: it won't be exactly 25% for each of them.  Because of the special X inheritance, your paternal grandfather will on average contribute slightly less than the other three grandparents.  (Because of another quirk, mitochondrial inheritance, your maternal grandmother will contribute on average a very small amount more than the other three grandparents.)