Pseudohypertrophic muscular dystrophy is a disorder that causes gradual deterioration of the muscles. It is seen only in boys born to apparently normal parents and usually results in death in the early teens.

A) Is this disorder caused by a dominant or a recessive allele?
B) Is its inheritance sex-linked or autosomal? How do you know?

C) Explain why this disorder is seen only in boys and never in girls.

Answered below

Explanation:

Pseudohypertrophic muscular dystrophy is also known as Duchenne muscular dystrophy. It is a rare genetic disease that primarily affects male children. It is characterized by progressive deterioration of muscle fibres leading to muscle weakness. This is the most common muscular dystrophy.

A) Pseudohypertrophic muscular dystrophy is caused by a recessive allele.

B) The inheritance of this disease is sex-linked because it is related to the sex chromosomes. It shows an inheritance pattern of one case in every 3,500 live male births.

C) Pseudohypertrophic muscular dystrophy is X-linked. It is seen primarily in boys because males have only one copy of the X chromosome. If the X chromosome has a gene mutation, the males will have the disease. Since females have two X chromosomes, one can compensate for the dysfunctional one.

It is caused by a recessive allele.

it is sex-linked. since it is seen only in boys this is an indication that it is present  on  X-chromosomes of the mother  and the boys must have inherited this from the mother. This is because the y chromosomes is weak and lacks allele.

Since most  boys with this disorders die in early  teens, then the presence of these allele in adulthood is rare. thus for a girl to inherit the gene, and  have this anomaly, she needs to inherit the recessive alleles from both parents. How  the inability of the male to grow to adulthood made the chances of this to be limited.

Explanation: