6Consider the following pedigree of a rare autosomal disease. Assume all people
ID: 3165210 • Letter: 6
Question
6Consider the following pedigree of a rare autosomal disease. Assume all people marrying into the pedigree do not carry the abnormal allele. [5 pts] (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 k D has the disease, what is the probability that their second child will have the disease?Explanation / Answer
a) the disease is recessive. It requires two alleles to express the phenotype. As we can see that A is phenotypically normal, whereras sister of A has the disease, meaning she get ony copy of the diseased allele from both the parents, whereas, A could have either one diseased allele or can be normal.
b) let assume the allele for the diease=a, normal allele= A
thus mother of B will have genotype aa, whereras father is AA
B who is a male will have the genotype=Aa
A who is a female has no chance of aa, or aa=0, then their is a chance of 2/3 rd that she is Aa or 1/3 rd of AA
now, if we take A is a carrier having the genotype Aa and B is also having the genotype Aa, then the chance of having a child with disease is or a child with aa genotype will be
2/3 X 1X 1/4= 1/6
c) Now, as A has the chance of 2/3 for heterozygous (Aa) then , C will 1/2 chance of being heterozygous ( Aa) as the father is AA. On the other hand D will also have 1/2 chance to be Aa. Thus the probability that they have a child with t9)he diesase or aa is 2/3 X 1/2 X1/2 X1X 1/4= 1/24.
d) the probability of the second child will also be same as 2/3 X 1/2 X1/2 X1X 1/4= 1/24, as every child birth is an independent event.
e) now, C= Aa and D= Aa, thus the probability that they have a second child with aa is 1/4.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.