Scientists Report Finding DNA Mutations That Caused Snakes to Lose Legs

A mutation in the DNA of some reptiles about 150 million years ago switched off the gene responsible for forming limbs — leading to the creation of modern day snakes, according to two studies published week. The findings were discovered by two independent teams of researchers, which reported their results separately in the journals Current Biology and Cell. Some snakes, including pythons and boas, still have tiny leg bones inside their bodies, remnants of this evolutionary history; but most species lost their legs starting about100 million years ago. The scientists traced the mutation back to a docking site for proteins, known as an enhancer, situated in front of the Sonic hedgehog gene, which controls limb development. They found that the enhancer is simply switched off, not broken. When the missing DNA was fixed and the modified enhancer was put in mice, they grew legs like normal.