A man and a woman, who do not show any apparent signs of a certain inherited disease, have seven children (2 d

Question

A man and a woman, who do not show any apparent signs of a certain inherited disease, have seven children (2 daughters and 5 sons). Three of the sons suffer from the given disease but none of the daughters are affected. Which of the following mode of inheritance might be the reason for this disease?

Accepted Answer

The inheritance pattern suggests a Sex-linked recessive trait (specifically X-linked). 
1. Recessive: Since the parents are unaffected (phenotypically normal) but have affected offspring, the trait must be recessive (eliminating dominant options). 
2. Sex-linked: The disease appears only in sons, while daughters remain unaffected. This is characteristic of X-linked recessive inheritance where the mother is a carrier (heterozygous). She passes the affected X chromosome to 50% of her sons, who express the disease because they have only one X chromosome. Daughters receive a normal dominant X chromosome from the unaffected father, preventing the expression of the disease .

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