Refer to figure 4, Mary and John both unaffected, have two sons and two daughter

Question

Refer to figure 4, Mary and John both unaffected, have two sons and two daughters; Janet, Sue, Jake, and Mark. Sue and Mark are unaffected, but Jake, Janet and one of Mark’s daughters are affected with an X-linked dominant disease (gene D). Which of the following is the correct conclusion about this family?

Mary is dd and John is d?; The mutation occurred in Mary’s germ cells

Mary is dd and John is D?; The mutation occurred in the germ cell of John’s mother

Mary is Dd and John is d?; The disease has not penetrated in Mary

Mary is dd and John is D?; The disease has not penetrated in John

Mary is Dd and John is D?; The disease has not penetrated in either of them

Sue is certainly Dd;The disease has not penetrated in her.

The disease certainly has not penetrated in three individuals of this family.

A.

Mary is dd and John is d?; The mutation occurred in Mary’s germ cells

B.

Mary is dd and John is D?; The mutation occurred in the germ cell of John’s mother

C.

Mary is Dd and John is d?; The disease has not penetrated in Mary

D.

Mary is dd and John is D?; The disease has not penetrated in John

E.

Mary is Dd and John is D?; The disease has not penetrated in either of them

F.

Sue is certainly Dd;The disease has not penetrated in her.

G.

The disease certainly has not penetrated in three individuals of this family.

Two of the above are correct.

Mary John ar Janet Sue Jake Figure 4

Explanation / Answer

Option c and g are correct because disease caused by dominant allele. And janet and jake, mark carry dominant allele from their mother who is carrier of the disease. other are not affected because they carry recessive allele.

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