, BIOL 331 Advanced Prep: Master
Genetics & Genetic Change Practice
Questions & Detailed Explanations
Subtopic: Genetic Change, Mutation, and Evolutionary Mechanisms
Question 1: A point mutation occurs in the third base of a codon, but the amino acid
sequence remains unchanged. Which of the following best describes this phenomenon and
its evolutionary significance?
A) This is a missense mutation that provides a substrate for natural selection.
B) This is a silent mutation; while it does not alter the protein phenotype, it may still affect
mRNA stability or splicing efficiency.
C) This is a frameshift mutation that usually results in a non-functional protein.
D) This is a nonsense mutation that terminates translation prematurely, potentially increasing
genetic diversity.
Correct Answer: B) This is a silent mutation; while it does not alter the protein phenotype, it
may still affect mRNA stability or splicing efficiency.
Explanation: A silent mutation involves a nucleotide substitution that results in the same amino
acid due to the degeneracy of the genetic code. While often considered "neutral," such mutations
can influence the rate of protein synthesis by affecting codon usage bias or alter secondary
mRNA structures, which in turn impacts splicing and transcript stability, potentially exerting
subtle fitness effects.
Question 2: In a population of beetles, a volcanic eruption randomly kills 80% of the
population, leaving a small group of survivors with a different allele frequency than the
original population. This is an example of:
A) Founder effect
B) Directional selection
C) Genetic bottleneck
D) Stabilizing selection
Correct Answer: C) Genetic bottleneck
,Explanation: A genetic bottleneck occurs when a significant percentage of a population is
eliminated due to a catastrophic event, drastically reducing the gene pool. The survivors
represent a random sample of the original population, leading to a shift in allele frequencies
independent of adaptive value, unlike natural selection.
Question 3: How does the "coding" vs. "non-coding" nature of DNA influence the
phenotypic impact of mutations?
A) Mutations in coding regions are always lethal, whereas non-coding mutations have no effect.
B) Mutations in non-coding DNA segments are more likely to have immediate effects on protein
folding.
C) Mutations in non-coding regulatory sequences can alter gene expression timing or spatial
localization without changing the protein primary structure.
D) Coding DNA is protected from mutations by specialized proteins, while non-coding DNA is
hyper-mutable.
Correct Answer: C) Mutations in non-coding regulatory sequences can alter gene expression
timing or spatial localization without changing the protein primary structure.
Explanation: Non-coding DNA often contains regulatory elements such as enhancers, promoters,
and silencers. Mutations here do not change the protein structure itself but can drastically
change when, where, and how much of a protein is produced, which is a major driver of
phenotypic variation and evolutionary divergence.
Question 4: Which of the following best distinguishes between somatic and germ-line
mutations?
A) Somatic mutations occur in gametes and are inherited by offspring.
B) Germ-line mutations occur in non-reproductive body cells and affect only the individual.
C) Somatic mutations arise post-conception and are not passed to the next generation, whereas
germ-line mutations are heritable.
D) Both mutation types have identical impacts on the evolutionary trajectory of a species.
Correct Answer: C) Somatic mutations arise post-conception and are not passed to the next
generation, whereas germ-line mutations are heritable.
Explanation: Somatic mutations affect only the cells descended from the mutated cell within the
individual’s body. Germ-line mutations occur in the cells that give rise to gametes (sperm and
eggs), ensuring that the mutation can be transmitted to the offspring and contribute to the
population’s gene pool.
, Question 5: What is the primary genetic consequence of an unequal crossing-over event
during meiosis?
A) A point mutation that creates a new allele.
B) The generation of gene duplications and deletions in the gametes.
C) A reduction in the overall chromosome number (aneuploidy).
D) The activation of transposable elements.
Correct Answer: B) The generation of gene duplications and deletions in the gametes.
Explanation: Unequal crossing-over occurs when homologous chromosomes misalign during
prophase I. This misalignment results in one chromatid receiving an extra copy of a gene
(duplication) while the other loses that gene (deletion), which is a primary mechanism for
increasing genetic raw material for evolution.
Question 6: In the context of biotechnology, what is the main purpose of "enucleation"
during Somatic Cell Nuclear Transfer (SCNT)?
A) To stimulate the somatic cell to begin mitosis before implantation.
B) To remove the endogenous genetic material from a recipient egg to ensure the clone matches
the donor somatic cell.
C) To introduce viral vectors into the donor cell's nucleus.
D) To select for diploid cells over haploid cells.
Correct Answer: B) To remove the endogenous genetic material from a recipient egg to
ensure the clone matches the donor somatic cell.
Explanation: In SCNT, the goal is to produce an organism genetically identical to the somatic
cell donor. Removing the nucleus from the recipient egg (enucleation) prevents the egg's original
genetic material from contributing to the development of the clone.
Question 7: Which of the following best describes the Founder Effect?
A) The change in allele frequency due to the migration of a large portion of the population.
B) The random loss of alleles when a small group of individuals colonizes a new, isolated
habitat.
C) The increase in fitness due to interbreeding between two different species.
Genetics & Genetic Change Practice
Questions & Detailed Explanations
Subtopic: Genetic Change, Mutation, and Evolutionary Mechanisms
Question 1: A point mutation occurs in the third base of a codon, but the amino acid
sequence remains unchanged. Which of the following best describes this phenomenon and
its evolutionary significance?
A) This is a missense mutation that provides a substrate for natural selection.
B) This is a silent mutation; while it does not alter the protein phenotype, it may still affect
mRNA stability or splicing efficiency.
C) This is a frameshift mutation that usually results in a non-functional protein.
D) This is a nonsense mutation that terminates translation prematurely, potentially increasing
genetic diversity.
Correct Answer: B) This is a silent mutation; while it does not alter the protein phenotype, it
may still affect mRNA stability or splicing efficiency.
Explanation: A silent mutation involves a nucleotide substitution that results in the same amino
acid due to the degeneracy of the genetic code. While often considered "neutral," such mutations
can influence the rate of protein synthesis by affecting codon usage bias or alter secondary
mRNA structures, which in turn impacts splicing and transcript stability, potentially exerting
subtle fitness effects.
Question 2: In a population of beetles, a volcanic eruption randomly kills 80% of the
population, leaving a small group of survivors with a different allele frequency than the
original population. This is an example of:
A) Founder effect
B) Directional selection
C) Genetic bottleneck
D) Stabilizing selection
Correct Answer: C) Genetic bottleneck
,Explanation: A genetic bottleneck occurs when a significant percentage of a population is
eliminated due to a catastrophic event, drastically reducing the gene pool. The survivors
represent a random sample of the original population, leading to a shift in allele frequencies
independent of adaptive value, unlike natural selection.
Question 3: How does the "coding" vs. "non-coding" nature of DNA influence the
phenotypic impact of mutations?
A) Mutations in coding regions are always lethal, whereas non-coding mutations have no effect.
B) Mutations in non-coding DNA segments are more likely to have immediate effects on protein
folding.
C) Mutations in non-coding regulatory sequences can alter gene expression timing or spatial
localization without changing the protein primary structure.
D) Coding DNA is protected from mutations by specialized proteins, while non-coding DNA is
hyper-mutable.
Correct Answer: C) Mutations in non-coding regulatory sequences can alter gene expression
timing or spatial localization without changing the protein primary structure.
Explanation: Non-coding DNA often contains regulatory elements such as enhancers, promoters,
and silencers. Mutations here do not change the protein structure itself but can drastically
change when, where, and how much of a protein is produced, which is a major driver of
phenotypic variation and evolutionary divergence.
Question 4: Which of the following best distinguishes between somatic and germ-line
mutations?
A) Somatic mutations occur in gametes and are inherited by offspring.
B) Germ-line mutations occur in non-reproductive body cells and affect only the individual.
C) Somatic mutations arise post-conception and are not passed to the next generation, whereas
germ-line mutations are heritable.
D) Both mutation types have identical impacts on the evolutionary trajectory of a species.
Correct Answer: C) Somatic mutations arise post-conception and are not passed to the next
generation, whereas germ-line mutations are heritable.
Explanation: Somatic mutations affect only the cells descended from the mutated cell within the
individual’s body. Germ-line mutations occur in the cells that give rise to gametes (sperm and
eggs), ensuring that the mutation can be transmitted to the offspring and contribute to the
population’s gene pool.
, Question 5: What is the primary genetic consequence of an unequal crossing-over event
during meiosis?
A) A point mutation that creates a new allele.
B) The generation of gene duplications and deletions in the gametes.
C) A reduction in the overall chromosome number (aneuploidy).
D) The activation of transposable elements.
Correct Answer: B) The generation of gene duplications and deletions in the gametes.
Explanation: Unequal crossing-over occurs when homologous chromosomes misalign during
prophase I. This misalignment results in one chromatid receiving an extra copy of a gene
(duplication) while the other loses that gene (deletion), which is a primary mechanism for
increasing genetic raw material for evolution.
Question 6: In the context of biotechnology, what is the main purpose of "enucleation"
during Somatic Cell Nuclear Transfer (SCNT)?
A) To stimulate the somatic cell to begin mitosis before implantation.
B) To remove the endogenous genetic material from a recipient egg to ensure the clone matches
the donor somatic cell.
C) To introduce viral vectors into the donor cell's nucleus.
D) To select for diploid cells over haploid cells.
Correct Answer: B) To remove the endogenous genetic material from a recipient egg to
ensure the clone matches the donor somatic cell.
Explanation: In SCNT, the goal is to produce an organism genetically identical to the somatic
cell donor. Removing the nucleus from the recipient egg (enucleation) prevents the egg's original
genetic material from contributing to the development of the clone.
Question 7: Which of the following best describes the Founder Effect?
A) The change in allele frequency due to the migration of a large portion of the population.
B) The random loss of alleles when a small group of individuals colonizes a new, isolated
habitat.
C) The increase in fitness due to interbreeding between two different species.
