Which of the following is part of the process of X chromosome inactivation?
A) Expression of Xist from both chromosomes at the start of the process
B) Binding of multiple Xist transcripts to Xic on the X chromosome that will be inactivated
C) Compaction of the active X chromosme into a Barr body
D) Binding of Tsix transcripts to the X chromosome to be inactivated after the Xist transcripts binds to Xic

Question

Quizplus · Accepted Answer

Xist (X-inactive specific transcript) gene is expressed only from the chromosome to be inactivated, and its transcript binds to the X-inactivation center (Xic), a cis-acting element in the same chromosome. Xist transcripts recruit additional factors and chromatin modifiers, leading to the formation of heterochromatin and transcriptional repression of most genes on that chromosome. Binding of multiple Xist transcripts to Xic is a critical step in the process of X chromosome inactivation.

A, C and D are incorrect choices. Expression of Xist gene is selective and only from the chromosome which needs to be inactivated. Compaction of the active X into Barr body occurs after the inactivation process. Binding of Tsix transcripts to the X chromosome is a regulatory step of the process, which occurs after the binding of Xist transcripts to Xic.

Which of the Following Is Part of the Process of X