Question

Mike and Mary are planning a family. In addition to their love for each other and for Game of Thrones, they have something else in common. They each have a history of cystic fibrosis in their family. Cystic fibrosis (CF) is an autosomal recessive disease.

i. Mary does not have CF, two of her three sisters have CF, and her mother didn’t have it. But her father did.

ii. Mike does not have CF, and two of his three brothers don’t either. But he has one brother with CF. Neither of his parents have CF.

iii. Your challenge is to determine: What is the probability that Mike and Mary's child would have CF? a.

Draw the Punnett squares for Mike and Mary’s families, as well as one for Mike and Mary’s future child. b. What is the probability that Mike and Mary's child would have CF? Show how you arrived at this numerical result. PLEASE HELP! Having trouble making the Punnett squares!!

Answer 1

As mike and Mary does not have the cystic fibrosis (CF) and if we observe the history of Mike and Mary families the siblings of mike and Mary have cysic fibrosis but Mike and Mary does'nt cystic fibrosis so Mike and Mary are the carries of the disease.

Cystic fibrosis (CF) is caused by a recessive allele. In the genetic diagram below, it is written as cf.

Punnette Square for Mary family

As Mary's mother does not have the cysytic fibrosis so she will be the carrier with the Cf trait. and Mary's father has the disease the recessive trait will be cf.

Punnette Square for Mary family	C	f
c	CC	cf
f	Cf	ff

So as per the punnett square in the f1 generation of Mary's family there are possibilities of two children with cystic fibrosis.

The phenotypic ratio will be 2:2 where 2 with cystic fibrosis and two with out cystic fibrosis.

Punnette Square for Mike's family

As Mike's mother and father does not have the cysytic fibrosis so they will be the carrier with the Cf trait.

Punnette Square for Mike's family	C	f
C	CC	Cf
f	Cf	ff

So as per the punnett square in the f1 generation of Mike's family there are possibilities of one child with cystic fibrosis.

The phenotypic ratio will be 1:3 where 1 with cystic fibrosis and 3 without cystic fibrosis.

Punnette Square for Mary nad Mike's future child

As Maey & Mike's cysytic fibrosis so they will be the carrier with the Cf trait.

Punnette Square for Mary nad Mike's future child	C	f
C	CC	Cf
f	Cf	ff

So as per the punnett square in the f1 generation there are possibilities of a one in four chance or 25 percent of the offspring being homozygous for the faulty allele, and so having cystic fibrosis..

The phenotypic ratio will be 1:3 where 25% with cystic fibrosis and 75% without cystic fibrosis.