Hi @ aatb294 In humans, the sex chromosomes determine whether a child will be born a boy or a girl. There are two types of sex chromosomes; X and Y. Females only have X chromosomes while males have both X and Y chromosomes. The child inherits these chromosomes from both parents. If the father’s sperm that fertilises the mother’s egg carries an X chromosome, the child is born female (XX), if the father supplies a Y chromosome, the child is born male (XY). The fact that males have both X and Y chromosomes makes people claim that the father determines the sex (boy or girl) of a child.
Some individuals can be intersex; they don’t fit well in our definitions of “boy” or “girl”. This could be due to abnormalities in the sex-chromosomes, reproductive organs or sex-related hormones.