Question

Duchenne muscular dystrophy is a sex-linked trait characterized by muscle degeneration that leads to a loss of skeletal muscle control, respiratory failure, and, eventually, death If a man who does not have Duchenne muscular dystrophy marries a woman who is a carrier for the trait, predict the genotype and phenotype for their offspring.

a. genotype of male
b. genotype of female
c. genotypes of offspring
d. phenotypes of offspring

Answer 1

If a man without Duchenne muscular dystrophy has children with a carrier woman, their sons have a 50% chance of being affected or non-affected and daughters have a 50% chance of being carriers. None of the daughters will be affected with DMD since it is an X-linked recessive disorder and girls would have one normal X chromosome from their father.

Step-by-step explanation:

Duchenne muscular dystrophy (DMD) is a sex-linked genetic disorder, primarily affecting males and caused by a mutation in a gene on the X-chromosome responsible for the production of the protein dystrophin. DMD leads to progressive muscle degeneration and weakness. When a non-affected man (genotype XY) marries a carrier woman (genotype XDXd), we can predict the possible genotypes and phenotypes of their offspring.

• Genotype of male: XY (non-affected)
• Genotype of female: XDXd (carrier)
• Genotypes of offspring: XX, XDY (male, non-affected), XdXD (female, carrier), XdY (male, affected with DMD)
• Phenotypes of offspring: 50% chance for a son to be non-affected and a 50% chance to have DMD (if male). Daughters have a 50% chance of being carriers like their mother, and a 50% chance of having two normal alleles if female.

Offspring will inherit an X chromosome from their mother and either an X or Y chromosome from their father. This dictates that sons have a 50% chance of having Duchenne muscular dystrophy if they inherit the Xd allele and daughters have a 50% chance of being carriers if they inherit the Xd allele. None of the children will have DMD if they inherit the normal X chromosome from their mother.