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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