You may see a connection between this post and the last one: thinking about sex determination and Owen Wilson. But I was wondering what determines male or female. Do you remember?
Answer: Human females contain two X chromosomes, and males contain one X and one Y
chromosome. In the absence of a Y chromosome, a human fetus will develop as a female.
This indicates that a gene or genes on the Y chromosome determines "maleness". Several
genes that are required for male development have been located on the Y chromosome, but
as far as I know, the "master" gene has not yet been identified.
taken from: this source