Direction: In the following questions a statement of assertion (A) is...
Haemophilia is a sex-linked recessive disorder in which X-chromosome has the haemophilic gene. A haemophilic father can never pass the gene for haemophilia to his son.
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Direction: In the following questions a statement of assertion (A) is...
The correct answer is option (d) Assertion (A) is false but reason (R) is true.
Explanation:
Haemophilia is an X-linked recessive disorder, not an autosomal disorder. It is caused by a mutation in the gene responsible for producing blood clotting factors, specifically factors VIII or IX. Since this gene is located on the X chromosome, haemophilia is inherited in an X-linked manner.
In an X-linked recessive disorder like haemophilia, the gene mutation is located on the X chromosome. Males have one X and one Y chromosome, while females have two X chromosomes. If a male inherits the defective gene from his mother, he will have haemophilia because he only has one X chromosome and there is no corresponding normal gene to compensate for the mutation. On the other hand, females need to inherit two copies of the defective gene (one from each parent) to have haemophilia. If they only inherit one copy, they will be carriers of the disorder but will not exhibit symptoms.
Therefore, the statement of assertion (A) is false because haemophilia is not an autosomal disorder.
However, the statement of reason (R) is true. A haemophilic father can never pass the gene for haemophilia to his son. This is because a father can only pass his Y chromosome to his son, not his X chromosome. Since the gene mutation for haemophilia is located on the X chromosome, it is not possible for a father with haemophilia to pass the gene to his son. The son will receive his X chromosome from his mother, who may be a carrier of the gene but does not have haemophilia herself.
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