A Barr body is a(n)?

Question

A) result of primary nondisjunction

B) inactivated Y chromosome

C) gene that plays a key role in male development

D) inactivated X chromosome

E) none of these

Answer 1

d

Answer 2

D is correct.

The Barr Body is the result of X inactivation, a process where all but one X chromosome in a mammalian cell becomes condensed and transcriptionally inactive (meaning genes on it are not expressed) in order to balance X chromosome gene expression between males and females.

The reason I say “but one X chromosome” is because in rare cases some individuals have 3, 4, or sometimes 5 X chromosomes. When this occurs each forms a Barr Body. It also happens in males should they inherit a second X chromosome (called Klinefelter's syndrome). These males will also have a Barr Body.

Answer 3

D) inactivated X chromosome

Answer 4

D.

Barr body is found the the somatic (body) cells of females only (since they have XX s*x chromosomes in their body cells, unlike males with XY chromosomes).

Answer 5

D)

the inactivation of X chromosomes, which is common in female.