試題詳解

13. All female mammals have one active X chromosome per cell instead of two. What causes this to happen?
(A) attachment of methyl (-CH3) groups to the X chromosome that will remain active
(B) only the X chromosome from mother will remain active
(C) inactivation of the XIST gene on the X chromosome derived from the male parent
(D) activation of the BARR gene on one X chromosome, which then becomes inactive
(E) activation of the XIST gene on the X chromosome that will become the Barr body