Hosted by Sandra Tsing Loh, The Loh Down on Science is a fun way to get your daily dose of science plus a dash of humor in less than two minutes.
Hosted by Sandra Tsing Loh
Airs Weekdays 2:31, 3:31 and 5:49 a.m.

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!