"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).

But that doesn’t always apply when it comes to categorizing people by their sex chromosomes. "You either have XX or XY chromosomes," Rep. Nancy Mace, R-S.C., wrote Feb. 20 on X. "Those are the ...

For years, the fact that women tend to outlive men has been a topic of interest and speculation among scientists and the ...

One X chromosome and one comparatively diminutive Y chromosome (XY), on the other hand, results in a male organism that produces smaller gametes, or sperm. Almost immediately, however, scientists ...

Scientists may have figured out why women live longer than men — linking it to having two X chromosomes, which defend against ...

the second X chromosome can have a protective effect and reduce the effects of a gene change on the first. However, when a person has XY chromosomes, that protective effect is lost. This is why ...