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Question
Presence of one Barr body in WBC indicates that the person is
Presence of one Barr body in WBC indicates that the person is
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Solution
The correct option is D Normal female
As we know that human females have two copies of X-chromosomes while the male has only single copy. To compensate the dosage of X-linked genes in human male and female, one X-chromosome in females is deactivated and is present as darkly stained body near nuclear envelope. The number of Barr bodies is always one less than the total number of X chromosomes. A human male with XY sex chromosomes lacks Barr body which makes option B wrong. A normal human female with XX sex chromosome has 1 Barr body; option C is correct. Both haemophilia and colour blindness are X-linked recessive disorders; a female needs two copies of the affected allele to express the disease which means that a haemophilic or colour blind woman has two active X-chromosomes and no Barr body; options A and D are incorrect.
As we know that human females have two copies of X-chromosomes while the male has only single copy. To compensate the dosage of X-linked genes in human male and female, one X-chromosome in females is deactivated and is present as darkly stained body near nuclear envelope. The number of Barr bodies is always one less than the total number of X chromosomes. A human male with XY sex chromosomes lacks Barr body which makes option B wrong. A normal human female with XX sex chromosome has 1 Barr body; option C is correct. Both haemophilia and colour blindness are X-linked recessive disorders; a female needs two copies of the affected allele to express the disease which means that a haemophilic or colour blind woman has two active X-chromosomes and no Barr body; options A and D are incorrect.
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