Friday, March 09, 2007

Those ain't just your daddy's genes (and maybe not your momma's)

You probably get half of your genes from your mother and half from your father, but it's possible that you got some of your genes from someone - or something - else.

A new model proposed by Jeong-Man Park of Rice University in Houston and his colleague Michael Deem (the same guy working on the HIV vaccination scheme I mentioned a few posts back) suggests that much a significant portion of our DNA was donated by viruses and bacteria that infected our ancestors over the ages. Although the chances are slim, it's possible that some of your DNA comes from microbes that infected your mother or father.

Park and Deem were led to the conclusion as they sought a theoretical answer to the question of why evolution proceeded fairly slowy for 2.5 billion years, as simple multi-cellular organisms developed, and then raced ahead for the next billion years to produce you and me and Brad and Angelina.

The answer may be horizontal gene transfer (HGT). When it was first proposed as a mechanism for bacteria to trade chunks of DNA and effectively adapt without reproducing, the idea of HGT was very controversial. By looking at common sections of DNA in species that should not be related, many scientists have come to the conclusion that we must be exhanging DNA through HGT. In fact, it seems to be at least as important for evolution as the passing on of mutations through sexual reproduction. Among other things, it appears that our immune systems arose from a gene transfer that must have occurred about 400 million years ago.

Park and Deem presented their model of HGT enhanced evolution in a paper published in the journal Physical Review Letters in January. In addition, Deem and Jun Sun (also of Rice University) presented a paper at this week's APS March meeting that shows how genes consist of modular chunks that lead to various traits, rather than having the genetic information spread throughout your genes. This modularity could be handy when it comes to swapping useful blocks of DNA.

1 comment:

amiya said...

Mitochondrial DNAs (mtDNA) are thought to have been incorporated in us from bacterias, long ago. These are DNAs found in the mitochondria, an organelle found in cells. We inherit this strip of DNA only from our mothers.