Duchenne Muscular Dystrophy (DMD) is a sex-linked characteristic encoded by the

Question

Duchenne Muscular Dystrophy (DMD) is a sex-linked characteristic encoded by the dystrophin gene found on the X chromosome. A mutation of the dystrophin gene causes issues in the structural support of muscle tissue. This disease affects 1 in 3,600 boys, resulting in muscle degeneration and eventual death. Paul has DMD and was fortunate to live to have children. He married Lisa at age 20, and they had two children, one normal boy and one diseased girl, before Paul passed away at age 25.

a. What are the genotypes and phenotypes of Paul and Lisa?

i. Given these data, would you expect Lisa’s family pedigree to show the presence of absence of DMD? Why or why not?

b. What are the genotypes and phenotypes of their children?

i. Given these data, should the son or daughter be most concerned about transmittance to offspring? Why?

Explanation / Answer

a. Genotype of Paul X• Y , phenoype diseased

Genotype of Lisa X• X , phenotype normal but carrier

1. One of Lisa's parent must be affected or carrier of DMD. If father carries the mutation in gene he must be diseased. But if her mother carries the mutation in gene she can be diseased or carrier .

b. Father X•Y × Mother XX•

   Son XY ,phenotype: normal(as information given)

   Daughter X•X• phenotype : diseased

1. Son is perfectly normal but the daughter is diseased and will pass her gene to next generation.

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