A new finding in mice rewrites the textbook explanation of the male sex-determining gene, Sry. It might also help us better understand how males and females come to be.
Birds have some of the most amazing sex differences of any animal. They can control the sex of offspring, and even produce rare half-male, half-females. And their sex genes and chromosomes are quite different from ours.
Many babies are born with a genetic variant that can result in the child being neither a typical boy or girl. There has been considerable debate about whether the child should be treated.