The neo-X (top) and neo-Y chromosomes of the fruit fly Drosophila miranda, showing how the Y has shrunken slightly through loss of genes. The X has remained about the same size as the fly’s other chromosomes, though its genes are in the process of adapting to the Y’s degeneration.
In the first evolutionary study of the chromosome associated with being female, University of California, Berkeley, biologist Doris Bachtrog and her colleagues show that the history of the X chromosome is every bit as interesting as the much-studied, male-determining Y chromosome, and offers important clues to the origins and benefits of sexual reproduction. The neo-X (top) and neo-Y chromosomes of the fruit fly Drosophila miranda , showing how the Y has shrunken slightly through loss of genes. The X has remained about the same size as the fly's other chromosomes, though its genes are in the process of adapting to the Y's degeneration. (Doris Bachtrog/UC Berkeley) "Contrary to the traditional view of being a passive player, the X chromosome has a very active role in the evolutionary process of sex chromosome differentiation," said Bachtrog, an assistant professor of integrative biology and a member of UC Berkeley's Center for Theoretical Evolutionary Genomics. Bachtrog, UC Berkeley post-doctoral fellow Jeffrey D. Jensen and former UC San Diego post-doc Zhi Zhang, now at the University of Munich, detail their findings in this week's edition of the open-access journal PLoS Biology. "In our manuscript, we demonstrate for the first time the flip side of the sex chromosome evolution puzzle: The X chromosome undergoes periods of intense adaptation in the evolutionary process of creating new sections of the genome that govern sexual differentiation in many species, including our own," she said.
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