By outfitting mice with a chunk of DNA that directs wing
development in bats, scientists have created rodents with
abnormally long forelimbs, mimicking one of the steps in the
evolution of the bat wing. Their work gives weight to the idea
that variations in how genes are controlled, and not just
mutations in the coding regions of genes, are a driving force in
evolution. The slightly longer forelimbs of the transgenic mice
"make them more batlike," says Nipam Patel, a professor of
molecular and cell biology and integrative biology at the
University of California, Berkeley, who was not involved in the
work. "It seems like a subtle difference, but evolution works by
these subtle differences." The researchers focused on a gene,
Prx1, that plays a part in the elongation of limb bones in
mammals. The gene's expression is regulated by another sequence
of DNA, called a Prx1 enhancer. To investigate how the enhancer
shapes limb development, Richard Behringer, a professor of
molecular genetics at the University of Texa