THE paradox that complex creatures often have less DNA than simple ones could
be a result of chance mutation.
Differences in genome size are often attributed to natural selection, so
Dmitri Petrov and his colleagues at Harvard University decided to test this by
comparing the fate of useless or 鈥渏unk鈥� DNA in Drosophila flies with
that in Laupala crickets (Science, vol 287, p 1060).
The cricket鈥檚 genome is 11 times as large as the fly鈥檚. If the difference was
the result of natural selection, mutations involving DNA deletion should happen
at the same rate in each and flies with smaller genomes would be more likely to
survive. But the researchers found that large deletions of junk DNA happened
more often in flies than in crickets. Petrov now hopes to study other species.
鈥淲e want to answer how much of the variation in genome size can be explained by
mutation patterns,鈥� he says.
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