Chromosomes are structures found in the center (nucleus) of
cells that carry long pieces of DNA. DNA is the material that
holds genes. It is the building block of the human body.
Chromosomes also contain proteins that help DNA exist in the
proper form. Chromosomes come in pairs. Normally, each cell in
the human body has 23 pairs of chromosomes (46 total
chromosomes). Half come from the mother; the other half come
from the father. Two of the chromosomes (the X and the Y
chromosome) determine if you are born a boy or a girl (your
gender). They are called sex chromosomes: Females have 2 X
chromosomes. Males have 1 X and 1 Y chromosome. The mother gives
an X chromosome to the child. The father may contribute an X or
a Y. It is the chromosome from the father that determines if the
baby is a girl or a boy. The remaining chromosomes are called
autosomal chromosomes. They are known as chromosome pairs 1
through 22. Stein CK. Applications of Cytogenetics in Modern
Pathology. In: McPherson RA, Pincus MR, eds.Henry's Cl