Like most theories for how new genes evolve, their common fate is to wither by disabling mutations. For a new gene to persist, its function must give an advantage to the organism -- and the earlier the better for the gene to avoid bad mutations. In Daphnia's case, there seems to be a sufficiently large pool of young gene copies that some will be expressed in novel circumstances, and by chance be compatible with expression patterns of interacting genes required to perform its new function.
"At first glance, amplified gene families in Daphnia are more likely to be functionally related than not," said Michael Lynch, coauthor and distinguished professor of biology at IU Bloomington. "This suggests that gene functions via duplication often evolve in cooperation with other genes in the genome. We are not yet prepared to generalize our findings until we broaden our investigation to include more Daphnia lineages having different population histories. However, it's quite clear that this genome project opens up enormous opportunities that are not readily accomplished using other models with poorly understood -- and not terribly accessible -- ecologies."
So what other reasons might Daphnia have so many genes compared to other animals? The coauthors of the Science paper begin addressing that issue as well as others related to the genomic architecture and evolution of the species.
"We don't yet have final answers," Pfrender said. "The sequenced isolate did originate from a naturally inbred population, which may contribute to some features of this genome -- and Daphnia's partial asexuality may have a hand to play."
Another possibility, Colbourne said, is that "since the majority of duplicated and unknown genes are sens
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