Download Practice Problems

Practice Problems
Accelerated Biology
Name _______________________________
1. A gardener has two tall pea plants. How can the gardener determine whether the two plants are
homozygous or heterozygous for the gene determining tallness?
____________________________________________________________________________________
Show the two Punnett squares as evidence for your conclusion. What is this type of cross called?
2. In rabbits the allele for black coat color (B) is dominant over the allele for white coat color (b). What
would be the result of a cross between an animal homozygous for black coat color (BB) and one
homozygous for white coat color (bb)? Show the gametes, Punnett square, and phenotypic and
genotypic ratios.
3. In guinea pigs the allele for rough coat (R ) is dominant over the allele for smooth coat (r ). In order
for all the offspring to be smooth coated, what should the phenotype and genotype of the male and
female parents be? Show the Punnett square to support your answer.
4. In Japanese four o’clocks the alleles for red flower color (R) and for white flower color (R’) are
examples of incomplete dominance. Thus a plant with the phenotype RR’ will have pink flowers. Show
the Punnett square and genotypic and phenotypic ratios for a cross between a plant with red flowers and
one with pink flowers.
5. In peas the allele for axial flowers (A) is dominant over the allele for terminal flowers (a). The allele for
inflated seed pods (I) is dominant over that for constricted pods (i). A cross between two peas with axial
flowers and inflated pods gives the following offspring:
20 with axial flowers and inflated pods
7 with axial flowers and constricted pods
5 with terminal flowers and inflated pods
1 with terminal flowers and constricted pods
What is the most probable genotype for the two parents? _____________________ Explain the results
and show the Punnett square.
6. For question 5 give all the possible crosses between two peas with axial flowers and inflated pods.
7. What would be the results of a cross between two pea plants that were heterozygous for both tall plants
and round seeds? Show the Punnett square, and state the genotypic and phenotypic ratios.
8. In rabbits the allele for black coat color (B ) is dominant over the allele for white (b). The allele for
straight hair (S) is dominant over curly hair (s). Someone gives you a male rabbit with black straight
hair and a female with white curly hair. If you bred these two, would you expect to get any white haired
curly rabbits in the first generation? Explain your answer with a Punnett square.
9. CRITICAL THINKING: The law of independent assortment applies not only to genetics but also to games
of pure chance. Suppose that you have 10 Ping Pong balls in a jar, each with a number from 1 to 10. If you
mix them thoroughly and take out one, the chances are 1 in 10 that you will get a particular number, for
example 5. If you have two such jars, the chances of drawing a 5 from each jar is 1 in 100 (1 in 10 for each jar,
or a total of 1 in 100 for drawing 5 & 5). Suppose that you have 5 such jars. What is the chance of drawing the
number 31456?