[Free Registration/Login may be required to access all resource tools.] What determines if a baby is a male or female? Recall that you have 23 pairs of chromosomes-and one of those pairs is the sex chromosomes. Everyone has two sex chromosomes. Your sex chromosomes can be X or Y. Females have two X chromosomes (XX), while males have one X chromosome and one Y chromosome (XY). Learn more about sex-linked inheritance in this learning module produced by CK-12.