Task II.5 In the pedigree below, the people who are shaved suffer from the same

Question

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) A1A2 are codominant and are expressed equally and there is risk of getting the disease. There is no crossover as the genes are linked genes.

b. The probability of the IV-1 becomes ill is 50% as in the second generation, the female with genotype A2A2(II-5) is not affected but the male with genotype A2 A2(II-7) is affected.

c) The probability of the IV-1 becomes heterozygous for the disease is also 50% .

d) The probability of the IV-1 becoming ill changes if the distance between the genes changes to few centimeters as there is chances for the crossing over between the genes and there is chance for the genes to be separated during crossing over.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.