The diagram below is a pedigree of three generations showing the occurrence of t
ID: 55811 • Letter: T
Question
The diagram below is a pedigree of three generations showing the occurrence of two genetically-transmitted
diseases. Phenotypes of affected individuals are shown. Circles represent females, and squares represent males.
Assume that the diseases are rare, unlinked, and that individuals not blood related to I-a sad I-b (“in-laws") do not have either disease-producing allele. Please answer why for each answer.
1. Which one of the following is true concerning Individual I-a? & why?
a. He is homozygous for Disease 1. and the allele for this disease is autosomal recessive.
b. He is heterozygous for Disease 1. and the allele for this disease is X-linked recessive.
c. He is heterozygous for Disease 1. and the allele for this disease is dominant.
d. He is heterozygous for Disease 1. and the allele for this disease is recessive.
e. Cannot be determined from the information gives
2. The genotype of Individual l-h for Disease 2 is: & why?
a. homozygous recessive.
b. heterozygous.
c. homozygous dominant.
d. spontaneous mutant
e. Not enough information to determine
3. lf Individual III - r marries a normal man with a homozygous wild-type genotype. what is the probability that their son would have Disease 2? & why?
a. 0
b. 1/4
c. 1/2
d. 3/4
e. 7/8
Generation Discase I --LheDc2 Disease 2 "Both diseasesExplanation / Answer
1. c
2. d
3. a