Evolution caught red-handed

Researchers have caught fruit fly evolution in flagrante delicto.

More specifically, in flagrante delicto Y, a newly described gene on the fruit fly Y chromosome. The gene appears to have been copied onto the sex chromosome from another fly chromosome around 2 million years ago, scientists report September 14 in the Proceedings of the National Academy of Sciences. Flagrante delicto Y is 98 percent identical to the gene from which it was copied, and the researchers believe that the new gene has a similar function: helping organize cells’ genetic material. Unlike its predecessor, flagrante delicto Y is expressed mainly in the testes.

The gene earned its scandalous moniker by providing concrete evidence of how Drosophila melanogaster’s Y chromosome picks up genes from other chromosomes. “Smoking gun Y” would have also been fitting, says study coauthor A. Bernardo Carvalho, a geneticist at the Universidade Federal do Rio de Janeiro. Adding genes allows the fly’s Y chromosome to grow larger and attain new abilities over millions of years. An opposite trend occurs in mammals’ Y chromosomes, which tend to lose genetic material as they evolve.