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The cells in females, with two X chromosomes, undergo X-inactivation, in which one of the two X chromosomes is inactivated.

The inactivated X chromosome remains within a cell as a Barr body.

Other less common chromosomal arrangements include: triple X syndrome, 48, XXXX, and 49, XXXXX.

In most mammals, sex is determined by presence of the Y chromosome.

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This and other factors result in the sex differences in humans.

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All animals have a set of DNA coding for genes present on chromosomes.

In humans, most mammals, and some other species, two of the chromosomes, called the X chromosome and Y chromosome, code for sex.

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