Biased Genes
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? Doh! It's like American Idol, but for genes!
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