http://primaryimmune.org/about-primary-immunodeficiencies/relevant-info/inheritance/
sex chromosome, either
of a pair of chromosomes that determine whether an individual is male orfemale.
The sex chromosomes of human beings and other
mammals are designated by scientists asX and Y.
In humans the sex chromosomes comprise one pair of the total of 23 pairs of
chromosomes. The other 22 pairs of chromosomes are called autosomes.
Individuals having two X chromosomes (XX) are female;
individuals having one X
chromosome and
one Y
chromosome (XY)
are male. The X chromosome resembles a large autosomal chromosome
with a long and a short arm. The Y chromosome has one long arm and a very short
second arm. This path to maleness or femaleness originates at the moment of meiosis,
when a cell divides to producegametes,
or sex cells having half the normal number of chromosomes. During meiosis the
male XY sex-chromosome pair separates and passes on an X or a Y to separate gametes;
the result is that one-half of the gametes (sperm) that are formed contains the
X chromosome and the other half contains the Y chromosome. The female has two X
chromosomes, and all female egg cells normally carry a single X. The eggs
fertilized by X-bearing sperm become females (XX), whereas those fertilized by
Y-bearing sperm become males (XY).
The Father can determine whether the parents will have a boy or not. Only the father can do this. The mother does not have the chromosome to have a boy. ( The Y chromosome= boy, comes from the father only. The mother has no y chromosome.)
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