Human Genetics: Concepts and Applications (Lewis), 9th Edition

Chapter 6: Matters of Sex

X inactivation

View the animation below, then complete the quiz to test your knowledge of the concept.


A Barr body is typically found in the nucleus of
A)female gametes only.
B)male gametes only.
C)female somatic cells only.
D)male somatic cells only.
E)both male and female somatic cells.

Which of the following statements about the Xist gene is TRUE?
A)It is located in the Xic region of the X chromosome.
B)It encodes an RNA that will coat an X chromosome to promote its compaction.
C)It functions in the initiation phase of X inactivation.
D)A and B
E)A, B and C

A cell with three X chromosomes will contain
A)no Barr bodies.
B)1 Barr body.
C)2 Barr bodies.
D)3 Barr bodies.
E)4 Barr bodies.

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

X chromosome inactivation equalizes the gene dosage between mammalian males and females.
Glencoe Online Learning CenterScience HomeProduct InfoSite MapContact Us

The McGraw-Hill CompaniesGlencoe