I need help with this task: II.5 because the last answer was wrong. Task II.5 In
ID: 202274 • Letter: I
Question
I need help with this task: II.5 because the last answer was wrong.
Task II.5
In the pedigree below, the people who are shaved suffer from the same rare autosomal recessive disease.
The married couple III-2 and III-3 await children together and seek to know what the risk is for their children to get the disease.
a) What is the risk assessed from the pedigree when ignoring the A-locus (see below)?
A polymorphic marker locus with two codominant alleles A1 and A2 is located so close to the disease focus that you can ignore crossovers. The genotypes of the A-locus are listed below the individuals in the pedigree that have been typed. Also on cells from the fetus IV-1, typing has been performed, and the genotype A2A2 was found.
b) What is the probability that IV-1 becomes ill if this information about A locus is involved?
c) What is the probability that IV-1 is heterozygous with respect to the disease gene (ie, carrier) under these conditions?
d) Would the probability of question b change (and if so, in what direction) if the distance between marker and disease focus instead was a few centimeters? Reason the answer!
Explanation / Answer
a)
The child of III 2 and 3 might bear any of the following genotypes A1A1, A1A2, A1A2, A2A2, Now we see two of the four are diseased conditions so there is a 50 percent chance that the child will be diseased.
b) if the genotype is A2A2, there is 100 percent chance that the child will be diseased
c) as per shown in a) there is a 50 percent chance of the child being heterozygous
d)Yes it would change as with increasing distance chances of recombination increase (crossover in Meiosis I). This will reduce the parental genotypes (Heterozygotes) and increase the recombinant (homozygotes) Thus chances of the child being diseased will increase.
A1 A2 A1 A1A1 (affected) A1A1(carrier) A2 A1A2 (carrier) A2A2 (affected)