In: Biology
Cystic fibrosis (CF) is a genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. CF is inherited in an autosomal recessive manner with simple Mendelian inheritance. It is caused by the presence of mutations in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. A normal couple intends to have children but consult a genetic counselor because the man has a sister with CF and the woman has a brother with CF. There are no other known cases in their family. They want to know: (1) What is the probability that their first child would be normal? (2) What is the probability that their first two children would have CF? (3) If they would like to have five children, what is the probability that at least two of them would be normal?
where R is other gene, r is recessive gene
so, their is 25% childern with disorder
75% childern does not have disorder
50% childern have gene like their parents.
25% childeren does not get gene from either parents.
As information given in the question we consider that normal couple have the gene locted on of the autosomes.
CF is inherited in an autosomal recrssive manner that means 2 copies of the genes is necessary to have genetic disorder.
Ans1. The probablity that their first child would be normal is 0.75 (3 out of 4).
Ans2. The probablity of first child would have CF is 0.25 (1 out of 4) so the probablity that their first two childern would have CF will be 0.125.
Ans 3. if they would like to have five childern so their will be total 32 combination of normal childern and diorder childern out of which 26 combination which have atleast two childern normal.
The probablity is 26/32 of haveng at least 2 childern normal.