6.Consider the following pedigree of a rare autosomal disease. Assume all people
ID: 187412 • Letter: 6
Question
6.Consider the following pedigree of a rare autosomal disease. Assume all people marrying into the pedigree do not carry the abnormal allele (a) is this disease dominant or recessive? (b) If individuals A and B have a child, what is the probability that the child will have the disease? (c) If individuals C and D have a child, what is the probability that the child will have the disease? (d) If the first child of C x D is normal, what is the probability that their second child will have the disease? (e)If the first child of C × D has the disease, what is the probability that their second child will have the disease?Explanation / Answer
a. The given pedigree represents an autosomal recessive inheritance pattern.
Reason: Phenotype is seen progeny even though it is not seen in the parents.
b.
The probability that A is a carrier = 2/3
The probability that B is a carrier = 1
The probability for their child to have the disease = 2/3 X 1 = 2/3 = 0.66 = 66%
c.
The probability that A is a carrier = 2/3
The probability that C is a carrier = 1/2
The probability that D is a carrier = 1/2
The probability for their child to have the disease = 2/3 X 1/2 X 1/2 = 0.166 = 16.6%
d.
The probability of second child to be affected is not different from the probability of the first child as both of these are random events.
= 16.6%
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