Poisons, antidotes, and selfish genes

Selfish genetic elements are parasitic replicators that are specialists in ensuring their own transmission despite conferring no benefit, or even exacting a cost, on their bearers. They come in many flavors, such as transposable elements, segregation distorters, female meiotic drivers, and so called B chromosomes (or accessory chromosomes)(1) . Such selfish elements provide the strongest support fort he gene centric view of evolution, as popularized by Richard Dawkins in The Selfish Gene (2) . On page1051 of this issue, BenDavid et al . (3) chase down a serendipitous observation of an anomaly in genetic crosses to unmask a toxin-antidote type of selfish system in worms. With the exception of transposable elements, which are abundant and easy to detect, little is known about the genetics of many broad classes of selfish genetic elements and the strategies that they deploy to manipulate cellular processes to their own advantage. This is, however, beginning to change . When performing genetic crosses between strains of the worm Caenorhabditis elegans, BenDavidet al . observed something that looked suspiciously like the work of a selfish system. During crosses to specifically move a region on chromosome V from a standard laboratory strain isolated from Bristol, UK, into a Hawaiian strain of the same species, another unlinked region from chromosome III also persisted despite attempts to exclude it. Through a series of genetic analyses, the authors identified two neighboring genes—the embryonic lethal gene pha1 and a genet hat encodes a suppressor of pha1 called sup35—as perpetrating invasive spread of the chromosome III region

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