The Loh Down On Science

Biased Genes

Sometimes evolution gets sloppy.

Evolution gone sloppy? This is Sandra Tsing Loh with The Loh Down on Science.

Your genetic code is spelled out with the four-letter DNA alphabet. Each letter – G, C, A, or T – is paired with another.

Only two pairings are stable: G with C, and A with T. If another combination turns up – say, C with A – cellular repair mechanisms quickly change it.

But for some reason – scientists aren't sure why – more mismatches get swapped to GC than AT.

That inequality – "biased gene conversion" – flies in the face of evolution.

Why? Because even when organisms would benefit more from an AT at a given spot, cells favor GC.

It's like always adding extra salt to your recipes – when sometimes sugar would taste better. Obnoxious!

A recent Swedish-American study compared the human genome to genomes of more ancient primates.

One big difference? Humans have lots more unwanted GCs gunking up our genes – each representing a possible misstep along the evolutionary path.

Survival of the fittest? Or just the most insistently wrong? D'oh! It's like American Idol, but for genes!


blog comments powered by Disqus