00:01
Hello students, cystic fibrosis is an autosomal recessive disorder.
00:23
It is given that carol and her sister is unaffected and her brother is affected person but her parents are also unaffected.
00:35
So as this is an autosomal recessive disorder, her parents has to be the carriers for the disease then only one of the children will be or any of the children will be affected.
00:47
So here we will shade half of the symbols so that it indicates they will be the carriers.
01:10
So these are carol's parents and they are having three children, her brother who is affected so we will shade it and her sister and carol herself so representing with c.
01:43
Then marcus we will represent him with m.
01:50
So marcus is having three sisters out of two are monocytotic twins so we will represent them like this and another sister also their parents are not affected because they don't have any family history of cystic fibrosis.
02:19
So this is the pedigree analysis for carol and marcus.
02:25
For the b part of the question, probability of having an affected child.
02:45
So here carol and marcus having an affected child we have to know the probability we need to consider their genotypes.
02:55
Carol's brother is having cystic fibrosis so small letter c then only he will be affected as it is an autosomal recessive disorder.
03:10
So we know that both of carol's parents are carriers of the disease that is capital c small c capital c small c.
03:21
Carol herself is not affected so she must be either a carrier or unaffected.
03:33
So two different types of genotypes are possible...