Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
X inactivation is a process by which one of the two X chromosomes in female mammals is randomly silenced to equalize gene expression with males. This results in a functional dosage compensation between males (XY) and females (XX).
5 Must Know Facts For Your Next Test
X inactivation occurs early in embryonic development.
The inactive X chromosome condenses into a structure known as a Barr body.
X inactivation is random, meaning either the maternal or paternal X chromosome can be inactivated.
Once an X chromosome is inactivated in a cell, all daughter cells will have the same X chromosome inactivated.
The gene XIST plays a crucial role in initiating the X-inactivation process.
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Related terms
Dosage Compensation: The mechanism by which organisms equalize the expression of genes between members of different biological sexes.
Barr Body: A dense, compact structure formed by the inactive X chromosome.
XIST Gene: A gene on the X chromosome responsible for triggering its own inactivation through RNA transcription.