Question

Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Due to the severity of the disease, the boys die in their teens. Is this disorder likely to be caused by a dominant or recessive allele? Is its inheritance sex-linked or autosomal?A) dominant, sex-linkedB) recessive, autosomalC) recessive, sex-linkedD) incomplete dominant, sex-linked

Answer 1

The answer is; C

It is caused by the recessive allele because the parents appear normal but are carriers of the disorder (meaning they are heterozygous for Pseudohypertrophic muscular dystrophy). Only when the offspring is heterogenous recessive do they display the disorder.

The disorder is also sex-linked because it tends to affect only boys. This means that the disorder is probably coded for by alleles in the Y- chromosome that determines the male sex.