In Female Humans and Other Mammals, Dosage Compensation Is Achieved

In female humans and other mammals, dosage compensation is achieved by the inactivation of one of the two X chromosomes in each cell. Which one of the following does NOT occur in the X-inactivation mechanism of female mammals?

A) X-inactivation begins with a small region of the X chromosome that contains a gene for an X- inactivation specific transcript (Xist) .
B) Xist is expressed in low levels except when an X chromosome is about to be inactivated.
C) When an X chromosome is about to be inactivated, Xist RNA transcripts increase markedly and undergo splicing, but do not encode a protein.
D) Xist RNA is attracted to and associates with a protein called the X-chromosome inactivation center (XIC) , which becomes entirely coated with Xist.
E) Xist RNA recruits factors that promote DNA methylation, histone modification, and other changes associated with transcriptional silencing.