YOU have probably heard of evolution in action - but how about evolution in reverse?
Many of the genes in our bodies have descended from ancient genes that have mutated and changed their function. Petr Tvrdik and Mario Capecchi of the University of Utah, Salt Lake City, have now managed to demonstrate this in mice by recreating an ancient gene from two of its modern descendants.
Half a billion years ago, the size of our ancestor's genome quadrupled. With four copies of every gene knocking about, genes either had to make themselves useful, or be swiftly dumped. The quadrupling meant that 13 Hox genes, which control the development of body shape, became 52. The ones that didn't mutate to do something useful were lost, so today mammals have 39 Hox genes.
Tvrdik and Capecchi focused on two that were originally duplicates but have evolved to perform different functions. Hoxa1 controls ...
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