Name ______Date ______

Period ______

Probability Problems

1. In humans, curly hair is dominant over straight hair. A woman heterozygous for hair curl

marries a man with straight hair and they have children.

a. What is the genotype of the mother? ______

b. What gametes can she produce? ______

c. What is the genotype of the father? ______

d. What gametes can he produce? ______

e. What is the probability that their first child will have curly hair? ______

f. What is the probability that their second child will have curly hair? ______

2. List all the gametes that are possible with each of the following genotypes:

a. Aabb ______d. AABb ______

b. AaBB ______e. AAbb ______

c. AaBb ______f. aabb ______

3. What is the probability of getting the gamete (ab) from each of the following parents?

a. Aabb ______d. AABb ______

b. aaBb ______e. AAbb ______

c. AaBb ______f. aabb ______

4. In a certain strain of mice, black coat (B) is dominant over white coat (b). Describe what you

would do to determine the genotype of a male with a black coat and how this would enable

you to choose between the genotypes BB or Bb.

______

______

______

______

5. What is the probability of each of the following sets of parents producing the given genotypes

in their offspring?

Parents’ Genotype / Offspring Genotype / Probability
Aa x Aa / Aa
Aa x aa / Aa
AaBb x AaBB / AABB
AaBb x AABb / aabb
AaBb x AaBb / AaBb

6. If an offspring has the genotype Aa, what possible combinations of parental genotypes could

have produced this offspring?

7. In corn, the trait for tall plants (T) is dominant to the trait for dwarf plants (t) and the trait for

colored kernels (C) is dominant to the trait for white kernels (c). In a particular cross of corn

plants, the probability of an offspring being tall is 1/2 and the probability of a kernel being

colored is 3/4. Which of the following most probably represents the parental genotype?

a. TtCc x ttCc

b. TtCc x TtCc

c. TtCc x ttcc

d. TTCc x ttCc

e. TTCc x TtCC

8. In humans, the allele for albinism is recessive to the allele for normal skin pigmentation.

a. If two heterozygous parents have children, what is the chance that the child will be

albino? ______

b. If the child is normal, what is the chance that it is a carrier (heterozygous) for the

albino allele? ______

c. If normal parents have an albino child, what is the probability that their next child will

be normal for pigment? ______

9. A student has a penny, nickel, a dime, and a quarter. She flips them all simultaneously and

checks for head or tails.

a. What is the probability that all four coins will come up heads? ______

b. She again flips all four coins. What is the probability that she will get four heads both

times? ______

10. What is the probability that, if three identical coins were flipped, all would end up heads?

______What is the probability that the three coins would not either be all heads or all

tails? ______

11.Flower position, stem length, and seed shape were three characters that Mendel studied. Each

is controlled by an independently assorting gene and has dominant and recessive expression

as follows:

Character / Dominant / Recessive
Flower position / Axial (A ) / Terminal (a )
Stem length / Tall (T ) / Dwarf (t )
Seed shape / Round (R ) / Wrinkled (r)

If a plant that is heterozygous for all three characters were allowed to self-fertilize, what

proportion of the offspring would be expected to be as follows: (Note - use the rules of

probability (and show your work) instead of huge Punnett squares)

a. homozygous for the three dominant traits ______

b. homozygous for the three recessive traits ______

c. heterozygous ______

d. homozygous for axial and tall, heterozygous for seed shape ______

12. What is the probability that each of the following pairs of parents will produce the indicated

offspring (assume independent assortment of all gene pairs)?

a. AABbCc x aabbcc ----> AaBbCc ______

b. AABbCc x AaBbCc -----> AAbbCC ______

c. AaBbCc x AaBbCc -----> AaBbCc ______

d. aaBbCC x AABbcc ----> AaBbCc ______

13. The genotype of F1 individuals in a tetrahybrid cross is AaBbCcDd. Assuming independent

assortment of these four genes, what are the probabilities that F2 offspring would have the

following genotypes?

a. aabbccdd ______

b. AaBbCcDd ______

c. AABBCCDD ______

d. AaBBccDd ______

e. AaBBCCdd ______

14. In a cross between a female AaBbccDdee and a male AabbCcDdee, what proportion of the

progeny will be the same phenotype as the female parent?

(Assume independent assortmentof all genes and complete dominance).