Aberrant appendages

Having a second pair of hands might seem like an advantage but animals born with extra limbs, because of changes in their DNA, generally do not fair well. For more than 25 years, scientists have known about the existence of a mutation in a fruit fly gene that causes just such aberrant appendages, yet the identity of this
gene remained a mystery.

That is until developmental biologist Jürg Müller and his team at EMBL Heidelberg set out to find the gene responsible. By comparing the DNA of mutant and normal flies, Jürg’s group pinpointed the mutation and found that it disrupts the genetic code for the protein Ogt, an enzyme that sticks sugar molecules to the outside of proteins.

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Pinning the tail on the histone

Nearly 60 years ago, Pamela Lewis, a geneticist at the California Institute of Technology in Pasadena, noticed that some of the flies she was experimenting on had tiny comb-like structures on their second and third pairs of legs, and not
just the first pair as is usual.

Lewis called these structures ‘sex-combs‘ because males use them to grasp females during mating and she went on to discover the first Polycomb gene, one of many such genes now known to encode proteins that disrupt head to-tail body patterning in a variety of animals, ranging from humans to fruit flies to worms.

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