genetics q - samomcos

[ArchivalUser]

a girl (with phenotypically normal parents and a brother with CF, marries a guy with CF (whose parents are phenotypically normal). What is the probability that their kid is going to have CF?
1) 100%
2) 66%
3) 50%
4) 33%
5) 25%

UW question... though i doubt the probability of them having a kid at all with the guy having CF.

[ArchivalUser]

25 %

[ArchivalUser]

am i right????

[ArchivalUser]

ANS.33%

[ArchivalUser]

is it 4==33%
if she s phenotypically normal then

chance of she will hav carrier==2/3
chance of she will inherit to d children=1/2

chance of her husband will inherit to d child=1

so probability of child will develop CF=2/3*1/2*1=1/3=33%

Correct me if i am wrong.

[ArchivalUser]

yup! 33% is right