Egg and sperm cells form through meiosis, a delicate process in which mistakes can later cause birth defects. Stanford researchers have now found that a key event in meiosis-a genetic shuffling called recombination-is started by the same protein in two very different organisms, yeast and worms. Given the evolutionary distance between yeast and worms, it seems likely that humans also use this mechanism, said the study's senior author, Anne Villeneuve.