BIOL 3301 Exam 4 Review Questions and 100% Correct Answers 2026/27 Update - UH
1. A population has two alleles at a single gene. Which of the following is least likely to
lead to a change in allele frequencies?
A. Natural selection in favor of one homozygote
B. Genetic drift
C. Inbreeding
D. All of the above are equally likely to change allele frequencies
E. None of the above will change allele frequencies
2. A species of mouse lives in a jungle. During one rainy season, a river forms through the
middle of the jungle. The river remains for many years. The animals within each side of
the river randomly mate with each other, but they cannot mate with the animals on the
other side. What do you expect to happen to allele and genotype frequencies in the
mouse populations on either side of the river?
A. Allele frequencies will differ between the populations on either side of the river,
and genotype frequencies will be out of Hardy-Weinberg equilibrium within each
population
B. Allele frequencies will differ between the populations on either side of the river,
and genotype frequencies will be in Hardy-Weinberg equilibrium within each
population
C. Allele frequencies will be the same between the populations on either side of the
river, and genotype frequencies will be out of Hardy-Weinberg equilibrium within
each population.
D. Allele frequencies will be the same between the populations on either side of the
river, and genotype frequencies will be in Hardy-Weinberg equilibrium within
each population.
E. Allele frequencies in one population will be the same as in the population before
the river formed.
3. Body color in a fish is controlled by one gene with two alleles. Homozygotes for one
allele and heterozygotes are bright red, whereas homozygotes for the other allele are
brown. You collect 100 individuals from a population and count 84 red individuals and
16 brown individuals. Assuming that the population is in Hardy-Weinberg equilibrium,
what is the frequency of the recessive allele?
A. 0.08
B. 0.16
C. 0.40
D. 0.60
E. 0.84
BIOL 3301 Exam 4
, 4. The brown fish from the previous question blend into the background and are less likely
to be eaten by predators than the red fish. Assuming the population mates at random, if
you came back in 5 generations and collected 100 more fish, what do you expect to
observe?
A. The recessive allele will have increased in frequency.
B. The dominant allele will have increased in frequency.
C. The allele frequencies will have not changed.
D. The allele frequencies will have changed, but we cannot predict how.
E. The genotype frequencies will no longer be Hardy-Weinberg equilibrium.
5. Researchers sequenced mitochondrial DNA (mtDNA) of 12 lions sampled from across
the world (H1-H12). They used the mtDNA sequences to construct the phylogeny
below.
Which of the following statements is most consistent with the tree?
A. Lions originated in Africa, and then they spread to Asia.
B. Lions originated in Asia, and then they spread to Africa.
C. Lions originated in Europe, and then they spread to Africa and Asia.
D. The North/Central African population is oldest.
E. None of these statements are consistent with the tree.
BIOL 3301 Exam 4
1. A population has two alleles at a single gene. Which of the following is least likely to
lead to a change in allele frequencies?
A. Natural selection in favor of one homozygote
B. Genetic drift
C. Inbreeding
D. All of the above are equally likely to change allele frequencies
E. None of the above will change allele frequencies
2. A species of mouse lives in a jungle. During one rainy season, a river forms through the
middle of the jungle. The river remains for many years. The animals within each side of
the river randomly mate with each other, but they cannot mate with the animals on the
other side. What do you expect to happen to allele and genotype frequencies in the
mouse populations on either side of the river?
A. Allele frequencies will differ between the populations on either side of the river,
and genotype frequencies will be out of Hardy-Weinberg equilibrium within each
population
B. Allele frequencies will differ between the populations on either side of the river,
and genotype frequencies will be in Hardy-Weinberg equilibrium within each
population
C. Allele frequencies will be the same between the populations on either side of the
river, and genotype frequencies will be out of Hardy-Weinberg equilibrium within
each population.
D. Allele frequencies will be the same between the populations on either side of the
river, and genotype frequencies will be in Hardy-Weinberg equilibrium within
each population.
E. Allele frequencies in one population will be the same as in the population before
the river formed.
3. Body color in a fish is controlled by one gene with two alleles. Homozygotes for one
allele and heterozygotes are bright red, whereas homozygotes for the other allele are
brown. You collect 100 individuals from a population and count 84 red individuals and
16 brown individuals. Assuming that the population is in Hardy-Weinberg equilibrium,
what is the frequency of the recessive allele?
A. 0.08
B. 0.16
C. 0.40
D. 0.60
E. 0.84
BIOL 3301 Exam 4
, 4. The brown fish from the previous question blend into the background and are less likely
to be eaten by predators than the red fish. Assuming the population mates at random, if
you came back in 5 generations and collected 100 more fish, what do you expect to
observe?
A. The recessive allele will have increased in frequency.
B. The dominant allele will have increased in frequency.
C. The allele frequencies will have not changed.
D. The allele frequencies will have changed, but we cannot predict how.
E. The genotype frequencies will no longer be Hardy-Weinberg equilibrium.
5. Researchers sequenced mitochondrial DNA (mtDNA) of 12 lions sampled from across
the world (H1-H12). They used the mtDNA sequences to construct the phylogeny
below.
Which of the following statements is most consistent with the tree?
A. Lions originated in Africa, and then they spread to Asia.
B. Lions originated in Asia, and then they spread to Africa.
C. Lions originated in Europe, and then they spread to Africa and Asia.
D. The North/Central African population is oldest.
E. None of these statements are consistent with the tree.
BIOL 3301 Exam 4
