Genetics Worksheet With Answer Key - Douglas J. Burks, Wilmington College Of Ohio Page 4

AbCd AbcD; 4 combinations of (dominant, dominant, dominant, recessive) ABCd,

aBCD, AbCD, ABcD 16 phenotypes.

b. aabbccdd x AABBCCDD

100% only one genotype in offspring.

c. AaBbCcDd x AaBbCcDd

16 phenotypes (2 x 2 x 2 x 2) all dominant would be (.75 X

.75 x .75 x .75) = .31 or 31% of offspring.

d. aabbccdd x aabbccdd

100% of offspring and only one phenotype

Problem #23. The achoo syndrome (sneezing in response to bright light) and trembling chin

(triggered by anxiety) are both dominant traits in humans.

a. What is the probability that the first child of parents who are heterozygous for both

the achoo gene and the trembling chin will have achoo syndrome but lack the

trembling chin?

Achoo is a .75 and trembling chin is therefore .25 so .75 x .25 =

18.75%

b. What is the probability that the first child will not have achoo syndrome or trembling

chin?

Non-achoo is .25 and normal chin is .25 therefore .25 x .25 =

0.0625 or 6.25%

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