John and Sue are expecting a child but are concerned about a

John and Sue are expecting a child, but are concerned about a rare autosomal recessive disease that is present in both of their families. In the pedigree below, John is represented as individual 111-11 and Sue is represented as individual 111-12. John\'s sister, 111-10, and Sue\'s brother, 111-13, both do not show evidence of the disease, but John\'s paternal grandmother and Sue\'s maternal grandfather both had the disease. Assign the appropriate symbol to each individual in the pedigree. What is the probability that neither John nor Sue is a carrier? What is the probability that John is a carrier?

Solution

Genotypes;

I-1 = AA/Aa

I-2 = aa

I-3 = aa

I-4 = AA/Aa

II-5 = Aa

II-6= Aa

II-7 =AA

II-8=Aa

III-9= aa

III-10= AA

III-11 =AA/Aa

III-12=AA/Aa

III-13= AA.

Probabailty that john is a carrier is 50%.