14. The mutation causing the recessive disease allele for sickle-cell anemia rem
ID: 63999 • Letter: 1
Question
14. The mutation causing the recessive disease allele for sickle-cell anemia removes one MstII restriction site from the globin gene so that a probe, instead of hybridizing to two fragments of 1.1 kb and 0.2 kb, hybridizes to one 1.3-kb fragment. For two parents to have a 25 percent chance of a child with sickle-cell anemia
A) they must both show only fragments of 1.1 and 0.2 kb.
B) they must both show fragments of 1.3 and 0.2 kb.
C) one must show only a 1.1- and the other only a 0.2-kb fragment.
D) one must show a 1.3- and the other a 1.1- and a 0.2-kb fragment.
E) they must both show all three types of fragments.
Explanation / Answer
Given that, the parents have a 25 percent chance of a child with sickle-cell anemia, means both are carriers. Observe the below cross between two carrier parents.
Ss* Ss = SS, Ss, Ss, ss (25% affected children).
B) they must both show fragments of 1.3 and 0.2 kb. (Since both carry the mutation).
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