Name: Mrs. Collins
How is a persons sex determined?
A person's sex is determined by the complement of sex chromosomes. Humans
normally have two sex chromosomes. Females have two X chromosomes, and males have one
X and one Y chromosome. Rarely, a person might be born with three sex chromosomes.
A person with XXY is a male, indicating that the presence of a Y chromosome (as opposed
to the presence of only one X) confers maleness. Presumably there is a master regulatory
gene on the Y chromosome that confers male sexual identity. In the absence of this
gene, the fetus will develop as a female.
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Update: June 2012