How Can Evolution Explain Opposite Genetic Effects?
To produce offspring, males and females contribute specialized reproductive cells called gametes–sperm cells from males and eggs from females. Most genes used to manufacture gametes differ from organism to organism. Scientists were surprised, therefore, by a recent study showing that, in spite of those differences, one gene in particular was present in all the animals surveyed. Since it codes for the protein Boule, the gene is also named Boule. The researchers performed a “knock-out” procedure, disabling Boule in mice. This rendered the males infertile. Fruit flies likewise become infertile when this gene is inactivated. In a separate study, other researchers replaced fruit fly Boule with human Boule, and the gene worked fine in the flies. Thus, “Boule is essential for male fertility,” because without it, sperm do not develop.1 By far, most genes involved in gamete formation are particular to each separate kind of animal, and only “a small handful” of genes were found in common among
