Letter S

Sex chromosome

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The X chromosome or the Y chromosome, in humans.

The sex chromosomes determine the sex of an individual.

As a general rule, normal females have two X chromosomes while normal males have an X and a Y chromosome.

The sex chromosomes evolved from an ancient pair of autosomal chromosomes.

The X is considerably larger and richer in genes than the Y.

The X contains 153 M bp (mega base pairs) and 1095 genes while the Y contains 50 M bp and 148 genes.

The sex chromosomes, by convention, are the 23rd and last pair of chromosomes in a normal human karyotype

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