Question

A male person having genes for childhood polycystic kidney disease was married to a lady who was diagnosed as carrier for colorblindness,they had 3 children,if two of them were normal,calculate the chance of the 3rd children to suffer from these diseases?

Calculate for the 3rd children to be boy and also in case of girl

Answer 1

For boys the chance is `50%` and for girls `0%`

None will suffer from Childhood Polycystic Kidney Disease

Explanation:

After we have finished the pedigree analysis we can see that the couple can have `8` types of children,i,e the 3rd children can be any of the `8` types shown below.

Considering about girls,

out of the `4` types of girls,one is absolutely normal,one is carrier of CPKD,one is carrier of colorblindness and the last one is carrier of both.

So,out of `4` none will be suffering from these two diseases,so probability of suffering of the 3rd child as a girl is `0`

Now,considering `4` boys, one is also absolutely normal,one is carrier of CPKD,one is colorblind and the last one is carrier of CPKD and colorblind at the same time.

So,out of `4` only `2` will be colorblind,so probability is `2/4=1/2=50%`

NOTE: None of the children will suffer from CPKD as all of them will receive one dominant normal gene from mother.