Question

Duchenne muscular dystrophy, or DMD, is the result of a recessive allele. If a woman with DMD and a man without DMD have children, all of the sons will have DMD, but none of the daughters will. Why does this occur?

DMD is sex-linked, and all daughters will inherit a dominant allele from their father.

DMD is sex-linked, and all sons will receive a recessive allele from their father.

Multiple alleles control the expression of DMD in daughters, who have two X chromosomes.

The normal allele expresses incomplete dominance over the allele for DMD in sons.

Answer 1

Answer

Option - DMD is sex-linked, and all daughters will inherit a dominant allele from their father.

Duchenne muscular dystrophy or DMD has a X-linked recessive pattern of inheritance. In the above given case, the father has normal X-chromosome which is dominant over the affected X chromosomes of the mother. Mother has 2 X chromosomes and both of them have the recessive allele.
This is why, all the daughters inherit the dominant non-affected gene from their father and are only carriers (Phenotypically normal) and all the sons inherit the recessive affected gene from their mother which will be expressed because they have only 1 X chromosome.