Question

If the father in a family has a disease while the mother is normal, the daughters only are inherited in this disease and not the sons. Name this type of disease.
(A) Autosomal recessive
(B) Autosomal dominant
(C) Sex-linked recessive
(D) Sex-linked dominant

Answer 1

Hint:
We already know that in a child half of set of the chromosomes comes from the father and the other half comes from the mother. Mother gives X chromosome to both sons and daughters whereas father gives Y chromosome to sons and X chromosome to their daughters.

Complete step by step solution:
If a father is affected by autosomal disorder whether it is recessive or dominant then it has equal chances of affecting both sons and daughters. Sex-linked disorders are the only ones which are passed on to only a specific gender from the father or mother.
So, if the disease is sex-linked recessive that means one recessive allele has to be received from both father and mother but here it is clearly mentioned in the question that the mother is normal.
If the disease is present on the X chromosome of the father and it is a dominant disorder then the father is affected and all his daughters are also affected for sure. So the correct answer to this question is sex-linked dominant.

Option ‘D’ is correct

Note:
Note that if a disease is passed on from the father to only sons and not his daughters then the disease is present in the Y chromosome of the father but if it is passed on to the daughter from a father then it has to be present in the X chromosome of the father.