YOU would probably expect worms in California and France to have different genes, even within one species. Not so for a stretch of chromosome from the laboratory workhorse Caenorhabditis elegans.
of Princeton University and his colleagues compared about 40,000 genetic markers from 97 wild strains collected around the world. Those on chromosome 5 were virtually identical in the vast majority of worms, they reported last week at .
Such a pattern can only be the result of strong natural selection for a gene, which would have caused all neighbouring genes to be selected as well.
Based on the size of this “selective sweep”, Shapiro calculates that the favoured gene variant arose 100 to 200 years ago and has since spread across the world, most likely by hitch-hiking with human migrations.
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“This is the first time we have seen a natural selective sweep of this much DNA,” says at Oregon State University in Corvallis.
