Question

You are consulting with a family where sometimes a mutation that leads to deafness (D) and a mutation that predisposes individuals to early heart failure (H) are linked. Normally these two traits sort independently but, in some individuals, a reciprocal translocation has moved them to the same chromosome. The chromosome maps for an individual with two normal chromosome pairs (Normal Arrangement), and a translocation heterozygote (Translocation Arrangement) are shown below. Deafness and early heart failure are both inherited in a dominant fashion (with respect to hearing and normal heart function). However, deafness is normally present at birth and early heart failure occurs on average at 40 years of age. A pedigree of the family is shown below. Below are chromosome maps (centromeres shown as blue dot) and pedigrees. Use what you know about translocation heterozygotes, and the chromosome maps and pedigrees, to answer the questions that follow. Note: The images are also in a separate PDF file (with text descriptions) posted under the Online Tutorial #2 link on Moodle. Normal arrangement Translocation arrangement DH ---> Chromosome with translocation I Chromosome with translocation 0 Q 0 FIL " O 1 O XXO 3 4 5 6 Del O Early heart failure € O 5 2

Answer 1

1.Only III-3 is translocation heterozygote. III-5 is not translocation heterozygote. One individual is translocation heterozygote and another is normal.

First option is the right one.

III-3 is translocation heterozygote and many of his gametes are not viable during meiosis.

2. Only one of the parents of III-3 is heterozygote for deafness and another parent is normal.

Since the individual is having fertility difficulties and is also deaf and translocation heterozygote, more likely chance that he will suffer from early heart failure.

Both are dominant and D, H are linked due to translocation. That is why if D is present since birth, you can expect H also to be presnt in the individual.