# 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

Mar 11, 2018

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.

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%