Mammals with multiple X chromosomes undergo random Xinactiva

Mammals with multiple X chromosomes undergo random X-inactivation in each nucleus early in gestational development. This results in only one X chromosome being active in each cell, no matter how many X chromosomes are present.Which sex chromosome genotype(s) would you expect to express Xist RNA?

Select all that apply.

a. XXXX

b. XXXY

c. XY

d. XX

Solution

The answers are

a. XXXX

b. XXXY and

d. XX

Xist (X-inactive specific transcript) is a RNA gene on the X chromosome of the placental mammals that acts as a major effector of the X inactivation process.