Questions 25 are based on the pedigree below The affected ph

Questions 2-5 are based on the pedigree below. The affected phenotype is due to an autosomal dominant gene. What is the genotype of individual II-1? aa AA Aa AA or Aa What is the genotype of individual II-3? aa Aa aa or Aa AA AA or Aa What is the probability that individual III-6 is homozygous? 0 1/4 1/3 1/2 2/3 3/4 What is the probability that individuals III-4 and III-5 will have a normal child? 1/6 1/4 1/3 3/8 1/2

Solution

Answer:

(2) a. aa

Parents = Aa or AA (Mother) x aa (father)

(3)c. AA or Aa

(4) b. ¼

Parents = Aa (Mother) x Aa (father)

F1: AA, Aa, Aa, aa

¼ are unaffected

(5) b. 1/4

III-4 (AA or Aa) x III-5 (aa)

F1: Aa, Aa, Aa,Aa, Aa, Aa, aa, aa

2/8 are unaffected

In autosomal dominant inheritance, only one copy of a disease allele is necessary for an individual to be susceptible to expressing the phenotype.

With each pregnancy, there is a one in two (50%) chance the offspring will inherit the disease allele.