OBJECTIVE LIFE SCIENCE
GENETICS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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His father
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His mother
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Either A or B
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None of the above
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Detailed explanation-1: -Son gets its X-chromosome from mother; since the male is affected, he has got the Xc allele from his mother. According to question, his parents are normal which means that father does not carry the disease; presence of disease in father would have expressed due to its hemizygous genotype for X-chromosome.
Detailed explanation-2: -This is due to the fact that males possess only a single X chromosome, and therefore require only one mutated X in order to be affected. Women possess two X chromosomes, and thus must receive two of the mutated recessive X chromosomes (one from each parent).
Detailed explanation-3: -X-linked recessive diseases most often occur in males. Males have only one X chromosome. A single recessive gene on that X chromosome will cause the disease.