True or false: Once a cell undergoes X chromosome inactivation, all of its daughter cells will have the same X chromosome inactivated.

True or false: Once a cell undergoes X chromosome inactivation, all of its daughter cells will have the same X chromosome inactivated.

• A. True
• B. False
• C. Not necessarily
• D. It varies by lineage

Answer: (A)

X inactivation creates a stable, heritable silent state on one of the X chromosomes in a female cell. Once a progenitor cell inactivates a particular X, the same X remains silenced in its daughter cells through successive cell divisions because the epigenetic marks that enforce silencing are replicated and maintained during mitosis. This makes the inactivation pattern effectively clonal: all descendants of that cell inherit the same X as inactive. There are special developmental contexts, like germ cell development, where X inactivation is reset, but for most somatic cell lineages the same X stays inactivated across the lineage. So the statement is true.

X inactivation creates a stable, heritable silent state on one of the X chromosomes in a female cell. Once a progenitor cell inactivates a particular X, the same X remains silenced in its daughter cells through successive cell divisions because the epigenetic marks that enforce silencing are replicated and maintained during mitosis. This makes the inactivation pattern effectively clonal: all descendants of that cell inherit the same X as inactive. There are special developmental contexts, like germ cell development, where X inactivation is reset, but for most somatic cell lineages the same X stays inactivated across the lineage. So the statement is true.