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

1 Answer
Mar 11, 2018

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

None will suffer from Childhood Polycystic Kidney Disease


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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.