X inactivation

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

1. X inactivation occurs early in embryonic development.
2. The inactive X chromosome condenses into a structure known as a Barr body.
3. X inactivation is random, meaning either the maternal or paternal X chromosome can be inactivated.
4. Once an X chromosome is inactivated in a cell, all daughter cells will have the same X chromosome inactivated.
5. The gene XIST plays a crucial role in initiating the X-inactivation process.

Review Questions

• What is the purpose of X inactivation?
• What structure does the inactive X chromosome form?
• Which gene is essential for initiating X inactivation?

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.