Natural Science Forum / Biology / Biology / January 2008

Hello, all!

I am posting this to sci.bio.misc because I don't know of a better
newsgroup in which to post; if anyone knows of a newsgroups which would be
better suited to my question, please let me know and I will post there.

I watch TV shows about forensics and DNA matches all the time, and I only
have a general college education on biology (I am a math and physics
undergrad working on a Ph.D in math), but it seems to me there is a
problem with the way DNA from sperm (or gametes in general) is matched to
the DNA of a suspect.

It is my understanding that when gametes are formed in meiosis, the
chromosomes exchange homologous genetic material, so that the DNA that
makes it into the gamete is *not* identical to one of the DNA strands in
the rest of the cells of the producer's body. This is a difference from
regular mitosis, where identical copies of the DNA strands are formed in
each of the resulting cells (mutations aside).

So, since the DNA strands in a gamete do not (almost surely) match the DNA
strands in, say, epithelial cells obtained from the donor due to the
exchange of genetic material, how is it possible to match donor of gamete
to the donor of a non-gamete?

Thank you in advance for any assistance you can provide.

Sincerely,