A hidden battle between X and Y chromosome-bearing sperm can sway the sex ratio of mouse litters. In a study published in Proceedings of the National Academy of Sciences, University of Michigan researchers uncovered the mechanism behind this microscopic arms race—where sperm compete for fertilization in a contest not unlike the race to the moon.
Mouse sperm rivalry may sway the sex of offspring
According to Martin Arlt, associate research scientist at the University’s Department of Human Genetics, whichever sperm, X- or Y-bearing, reaches the egg first is the one that successfully fertilizes it.