Genetics Worksheet With Answer Key - Douglas J. Burks, Wilmington College Of Ohio (Page 7 of 7) in pdf

Genetics Worksheet With Answer Key - Douglas J. Burks, Wilmington College Of Ohio Page 7

b is likely dominant since it does not skip generations. Every

individual showing the phenotype has at least one parent with the

trait.

C is likely recessive since it skips two generations.

Problem #31. A young couple went to see a genetic counselor because each had a sibling

affected with cystic fibrosis. (Cystic fibrosis is a recessive disease, and neither member of the

couple nor any of their four parents is affected.)

a. What is the probability that the female of this couple is a carrier?

If the female has a sibling with CF then her parents must

both be heterozygous CFcf x CFcf = .3 + .3 = 2/3 1:CFCF:

2:CFcf: 1 cfcf

b. What are the chances that their child will be affected with cystic fibrosis?

This is complicated.

odds of both being heterozygous is 4/9 (CFcf X CFcf)

If both parents are heterozygous then 25% chance of

offspring being affected. 4/9 x 25 is about 12%

c. What is the probability that their child will be a carrier of the cystic fibrosis mutation?

CFcf x CFcf

.5 x .44 = .22

2 CFcF x

.25 x .44 = .11 and two possibilities = .22

Total odd = .44 or 44%

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Genetics Worksheet With Answer Key - Douglas J. Burks, Wilmington College Of Ohio Page 7