In organisms like humans and mammals, the male is the heterogametic sex, producing gametes with either an X or a Y chromosome. All gametes from the female are X. Thus, the sex of the offspring is ...

XX-XY Athletics, a brand focused on protecting women's sports, released a video in which several athletes reacted to Nike's ...

"You either have XX or XY chromosomes," Rep. Nancy Mace, R-S.C., wrote Feb. 20 on X. "Those are the options." Most commonly, a person is born with two X chromosomes (female) or an X and a Y (male).

Physical gender is not always just a matter of XX or XY, girl or boy. In approximately one out of every 100 births, seemingly tiny errors occur during the various stages of fetal sex ...