BIOLOGY 100 - Human Biology

GENETICS PRACTICE PROBLEMS

Part 1

Question 1

For each of the diploid genotypes presented below, determine the genetic make up for all of the possible haploid gametes.

a. Rr

b. RrYy

c. rrYy

d. RrYY

e. RrYyBb

answer (click here)

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Question 2

Use the Punnett square to determine all of the offspring genotypes (and their relative frequencies) from the following crosses:

a. Rr x Rr

b. Rr x rr

c. RR x Rr

answer (click here)

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Question 3

In the problem above, the "R" allele is a dominant allele specifying for round seeds (in peas), while the "r" allele is the recessive allele specifying for wrinkled seeds. Give the expected frequencies (as percentages or ratios) for the phenotypes of the offspring resulting from each of the crosses above.

answer (click here)

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Question 4

A brown mink crossed with a silverblue mink produced all brown offspring. When these F1 mink were crossed among themselves they produced 47 brown animals and 15 silverblue animals (F2 generation). Determine all the genotypes and phenotypes, and their relative ratios, in the F1 and F2 generations.

answer (click here)

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Question 5

In sheep white is due to a dominant gene (W), black to its recessive allele (w). A white ewe mated to a white ram produces a black lamb. If they produce another offspring, could it be white? If so, what are the chances of it being white? List the genotypes of all animals mentioned in this problem.

answer (click here)

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Question 6

In tomatoes the texture of the skin may be smooth or peach (hairy). The Ponderosa variety has fruits with smooth texture. The red peach variety has fruits with peach texture. Crosses between the two varieties produce all smooth fruits. Crosses between these smooth fruited F1 plants produced 174 peach textured fruits and 520 smooth textured fruits. How are these skin textures inherited?

answer (click here)

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Question 7

A brown mouse is mated is mated with two female black mice. When each female has produced several litters of young, the first female has had 48 black and the second female has had 14 black and 11 brown young. Deduce the pattern of inheritance of coat color and the genotypes of all of the parents.

answer (click here)

 

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revised 21 August 2001