Principles of Inheritance and Variation Question 130

130. Barr body in human female is formed by

[1996]

(a) inactivation of paternal X-chromosome

(b) inactivation of maternal X-chromosome

(c) inactivation of both X-chromosomes

(d) inactivation of either the paternal or maternal X-chromosome

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Answer : d

Hints & Solution

(d) According to the principle of dosage compensation, one of the two $X$ chromosomes in a female is inactivated at random. The inactivated $X$ chromosome appears as the Barr body.