Question

‘A’ is mentioned as a trait carried by the father and passed to his sons only. What is the pattern of inheritance for this trait?

• A. ‘A’ is an allele carried on one of the mother’s autosomal chromosomes.
• B. ‘A’ is an allele carried on the Y-chromosome and passed on only to the sons.
• C. ‘A’ is an allele carried on the X-chromosome and can be directly inherited by the son from the father or the mother.
• D. ‘A’ is carried on the X-chromosome and can only be inherited by the son if the mother is a carrier.

Answer 1

The correct option is B ‘A’ is an allele carried on the Y-chromosome and passed on only to the sons.

‘A’ is an X-linked trait, and can only be inherited by the son from his mother’s X-chromosome. The father contributes the Y-chromosome to his son (not his X-chromosome) and thus cannot pass any of his X-linked alleles to his son.