*****tHE PEDIGREE IS CORRECT I JUST NEED HELP WITH THE PROBABILITY QUESTIONS. PL
ID: 53567 • Letter: #
Question
*****tHE PEDIGREE IS CORRECT I JUST NEED HELP WITH THE PROBABILITY QUESTIONS. PLEASE SHOW STEPS
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 III - 11 and Sue is represented as individual III - 12. John's sister, III-10, and Sue's brother, III-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 John is a carrier? What is the probability that neither John nor Sue is a carrier?Explanation / Answer
Answer
In the given pedigree, in the III generation one out of three indiviuals is affected that means both the aparents of this individual must be carriers of the disease. The individul III-3 (John) must be a carrier since he is not affected. So the probability of John being carrier of the recessibve allele is 2/3 or 66.7%.
If Sue's maternal grandfather had the disease and if her maternal garandmother is normal individual then the probability of Sue's father to be a carrier is 50% or 1/2. If Sue's mother is a normal individual and is not a carrier of the disease, then the probability of Sue being a carrier is o.5 x 0.5=0.25%
If Sue's mother is also a carrier, then the probability of Sue being a carrier for the recessive allele is 1/2 x 2/3=2/6 or 1/3.
The probability that both John and Sue are carriers is 2/3 x 1/3=2/9.
The probability that neither John nor Sue is a carrier is 2/3 x 1/4=16.6%
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