With the help of given pedigree, find out the probability for the birth of a child having no disease and being a carrier (has the disease mutation in one allele of the gene) in F3 generation. [figure]
- 1/8
- Zero
- 1/4
- 1/2
Answer
(3) 1/4
Solution
The affected F0 mother has only carrier daughters, and the disease reappears in a son (F2) of a carrier (unaffected) mother the trait is X-linked recessive.
Let Xa carry the mutation. The F2 parents of F3 are a carrier female XAXa and an affected male XaY.
XAXa XaY XAXa, XaXa, XAY, XaY, each with probability 14.
Only XAXa (carrier daughter) is free of the disease and carries the mutation.
Probability = 14
Answer: (3)