This page has been archived and is no longer updated. Whether an animal will become a male, a female, or a hermaphrodite is determined very early in development. Scientists have worked for hundreds of years to understand the sex-determination system. For instance, in B.
Chromosomal Sex Determination in Mammals - Developmental Biology - NCBI Bookshelf
A sex chromosome is a type of chromosome that participates in sex determination. Humans and most other mammals have two sex chromosomes, the X and the Y. Females have two X chromosomes in their cells, while males have both X and a Y chromosomes in their cells. Egg cells all contain an X chromosome, while sperm cells contain an X or Y chromosome. This arrangement means that it is the male that determines the sex of the offspring when fertilization occurs.
NCBI Bookshelf. Primary sex determination is the determination of the gonads. In mammals, primary sex determination is strictly chromosomal and is not usually influenced by the environment.
Humans are born with 46 chromosomes in 23 pairs. Most women are 46XX and most men are 46XY. Research suggests, however, that in a few births per thousand some individuals will be born with a single sex chromosome 45X or 45Y sex monosomies and some with three or more sex chromosomes 47XXX, 47XYY or 47XXY, etc. In addition, some males are born 46XX due to the translocation of a tiny section of the sex determining region of the Y chromosome.