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Inactive X Chromosome

Inactive X Chromosome
Inactive X Chromosome

One of the two X chromosomes in females is turned off through a process called X inactivation. On the right, a microscopic specimen of a cell nucleus from a female shows this inactive X chromosome as a dense lump (arrow). On the left, a specimen from a male is shown for comparison.

Courtesy of Drs. L. Carrell and H. Williard, Case Western Reserve University School of Medicine.