Question

Barr bodies are studied in

• A. Prophase nuclei of human female
• B. Interphase nuclei of human female
• C. Prophase nuclei of human male
• D. Interphase nuclei of human male

Answer 1

The correct option is B Interphase nuclei of human female

Barr body is an inactive X chromosome which becomes tightly coiled into heterochromatin in early embryo genesis. The dosage compensation to balance the dosage of X chromosome genes between XY males and XX females is accomplished by the inactivation of one of the X chromosomes in females. Barr body is found attached to nuclear membrane. The prophase nucleus does not have nuclear membrane or have disintegrated pieces of the membrane while the interphase nucleus show intact nuclear membrane to which Barr body is found attached. This is the reason that Barr bodies are not observed in prophase nucleus but in interphase nucleus. Human males have XY sex chromosomes and females have XX sex chromosomes. The number of Barr bodies is one less than the total number of X chromosomes. Hence, a female with 2 X chromosomes (XX) will have 1 Barr body and male with one X-chromosome have no Barr body at all. Hence Barr bodies are not observed in male having XY sex chromosomes. Correct answer is option B.