PORTAGE LEARNING BIOD 210 GENETICS FINAL EXAM
QUESTIONS WITH ANSWERS AND EXPLANATIONS
Question 1.
How is Locus best described?
A. A situation in which the phenotypic effect of a genotype depends on environmental
conditions
B. A species used experimentally because its biology allows efficient study of broadly
applicable genetic principles
C. The transmission of genetic information and traits from parents to offspring
D. The physical position of a gene or genetic marker on a chromosome
Correct Answer: D. The physical position of a gene or genetic marker on a
chromosome
Explanation: Locus is the physical position of a gene or genetic marker on a
chromosome. In this item, the key clue is that a disease-associated gene is mapped to a
defined chromosomal region. A useful distinguishing feature is that different alleles of the
same gene occupy the same locus on homologous chromosomes. The other choices
describe related ideas, but they do not match this full combination of definition, evidence,
and distinguishing feature.
Question 2.
Two clues are present: a histidine-requiring bacterial strain regains growth on
histidine-free medium after exposure to a test chemical, and increased revertant colonies
suggest the chemical or a metabolite can induce mutations. Which interpretation is best?
Choose the most precise course-level interpretation.
A. Klinefelter syndrome
B. Chromosomal duplication
C. Ames test
D. Mitochondrial inheritance
Correct Answer: C. Ames test
Explanation: Ames test is a bacterial assay used to screen chemicals for mutagenic
potential by measuring mutation-dependent reversion. In this item, the key clue is that a
histidine-requiring bacterial strain regains growth on histidine-free medium after exposure
to a test chemical. A useful distinguishing feature is that increased revertant colonies
suggest the chemical or a metabolite can induce mutations. The other choices describe
related ideas, but they do not match this full combination of definition, evidence, and
distinguishing feature.
,Question 3.
Which answer best integrates the observation that AB blood type expresses both A and B
antigens on red cells with the distinguishing point that codominance differs from
incomplete dominance because the two products remain individually detectable rather
than blending?
A. Dihybrid cross
B. Codominance
C. Testcross
D. Pedigree analysis
Correct Answer: B. Codominance
Explanation: Codominance is an allelic relationship in which both alleles are distinctly
expressed in the heterozygote. In this item, the key clue is that AB blood type expresses
both A and B antigens on red cells. A useful distinguishing feature is that codominance
differs from incomplete dominance because the two products remain individually
detectable rather than blending. The other choices describe related ideas, but they do not
match this full combination of definition, evidence, and distinguishing feature.
Question 4.
Which concept best accounts for both the observation that a prophage remains silent
through many bacterial divisions before induction and the fact that environmental stress
can trigger transition from lysogeny to productive lytic growth? Choose the most precise
course-level interpretation.
A. Replica plating
B. Lysogenic cycle
C. Transformation
D. Bacterial recombination
Correct Answer: B. Lysogenic cycle
Explanation: Lysogenic cycle is a phage state in which viral DNA integrates or persists in
the host and replicates with the bacterium without immediate lysis. In this item, the key
clue is that a prophage remains silent through many bacterial divisions before induction. A
useful distinguishing feature is that environmental stress can trigger transition from
lysogeny to productive lytic growth. The other choices describe related ideas, but they do
not match this full combination of definition, evidence, and distinguishing feature.
Question 5.
The finding that individuals with the same susceptibility allele show different outcomes
under different exposures is an example of which concept?
A. F1 generation
B. Genotype
C. Phenotype
D. Gene-environment interaction
Correct Answer: D. Gene-environment interaction
,Explanation: Gene-environment interaction is a situation in which the phenotypic effect
of a genotype depends on environmental conditions. In this item, the key clue is that
individuals with the same susceptibility allele show different outcomes under different
exposures. A useful distinguishing feature is that genetic influence does not mean a
phenotype is independent of environment. The other choices describe related ideas, but
they do not match this full combination of definition, evidence, and distinguishing feature.
Question 6.
A practical example involves a situation in which a tumor suppressor promoter becomes
heavily methylated and gene expression falls without a DNA-sequence mutation. Which
concept is being applied?
A. Proto-oncogene
B. Precision oncology
C. DNA methylation
D. Tumor suppressor gene
Correct Answer: C. DNA methylation
Explanation: DNA methylation is an epigenetic modification often associated with
reduced transcription when concentrated in gene regulatory CpG regions. In this item, the
key clue is that a tumor suppressor promoter becomes heavily methylated and gene
expression falls without a DNA-sequence mutation. A useful distinguishing feature is that
epigenetic silencing can contribute to cancer while remaining potentially reversible. The
other choices describe related ideas, but they do not match this full combination of
definition, evidence, and distinguishing feature.
Question 7.
A practical example involves a situation in which an individual carries A on one homolog
and a on the other. Which concept is being applied?
A. Genotype
B. Heterozygous genotype
C. Locus
D. F1 generation
Correct Answer: B. Heterozygous genotype
Explanation: Heterozygous genotype is a genotype containing two different alleles at a
locus in a diploid organism. In this item, the key clue is that an individual carries A on one
homolog and a on the other. A useful distinguishing feature is that under complete
dominance the dominant phenotype can conceal the recessive allele. The other choices
describe related ideas, but they do not match this full combination of definition, evidence,
and distinguishing feature.
, Question 8.
Which concept is most directly represented when a histidine-requiring bacterial strain
regains growth on histidine-free medium after exposure to a test chemical? Choose the
most precise course-level interpretation.
A. Chromosomal duplication
B. Chromosomal deletion
C. Silent mutation
D. Ames test
Correct Answer: D. Ames test
Explanation: Ames test is a bacterial assay used to screen chemicals for mutagenic
potential by measuring mutation-dependent reversion. In this item, the key clue is that a
histidine-requiring bacterial strain regains growth on histidine-free medium after exposure
to a test chemical. A useful distinguishing feature is that increased revertant colonies
suggest the chemical or a metabolite can induce mutations. The other choices describe
related ideas, but they do not match this full combination of definition, evidence, and
distinguishing feature.
Question 9.
Which concept should be selected for the observation that a single tRNA species can
decode several codons differing at the third base?
A. Transfer RNA
B. DNA helicase
C. Wobble base pairing
D. RNA polymerase
Correct Answer: C. Wobble base pairing
Explanation: Wobble base pairing is flexible pairing at the third codon position that
allows one tRNA to recognize more than one synonymous codon. In this item, the key clue
is that a single tRNA species can decode several codons differing at the third base. A
useful distinguishing feature is that wobble contributes to degeneracy of the genetic code
without altering the encoded amino acid. The other choices describe related ideas, but
they do not match this full combination of definition, evidence, and distinguishing feature.
Question 10.
Which concept best accounts for both the observation that a prophage remains silent
through many bacterial divisions before induction and the fact that environmental stress
can trigger transition from lysogeny to productive lytic growth?
A. Lysogenic cycle
B. Specialized transduction
C. Transduction
D. Horizontal gene transfer
Correct Answer: A. Lysogenic cycle
QUESTIONS WITH ANSWERS AND EXPLANATIONS
Question 1.
How is Locus best described?
A. A situation in which the phenotypic effect of a genotype depends on environmental
conditions
B. A species used experimentally because its biology allows efficient study of broadly
applicable genetic principles
C. The transmission of genetic information and traits from parents to offspring
D. The physical position of a gene or genetic marker on a chromosome
Correct Answer: D. The physical position of a gene or genetic marker on a
chromosome
Explanation: Locus is the physical position of a gene or genetic marker on a
chromosome. In this item, the key clue is that a disease-associated gene is mapped to a
defined chromosomal region. A useful distinguishing feature is that different alleles of the
same gene occupy the same locus on homologous chromosomes. The other choices
describe related ideas, but they do not match this full combination of definition, evidence,
and distinguishing feature.
Question 2.
Two clues are present: a histidine-requiring bacterial strain regains growth on
histidine-free medium after exposure to a test chemical, and increased revertant colonies
suggest the chemical or a metabolite can induce mutations. Which interpretation is best?
Choose the most precise course-level interpretation.
A. Klinefelter syndrome
B. Chromosomal duplication
C. Ames test
D. Mitochondrial inheritance
Correct Answer: C. Ames test
Explanation: Ames test is a bacterial assay used to screen chemicals for mutagenic
potential by measuring mutation-dependent reversion. In this item, the key clue is that a
histidine-requiring bacterial strain regains growth on histidine-free medium after exposure
to a test chemical. A useful distinguishing feature is that increased revertant colonies
suggest the chemical or a metabolite can induce mutations. The other choices describe
related ideas, but they do not match this full combination of definition, evidence, and
distinguishing feature.
,Question 3.
Which answer best integrates the observation that AB blood type expresses both A and B
antigens on red cells with the distinguishing point that codominance differs from
incomplete dominance because the two products remain individually detectable rather
than blending?
A. Dihybrid cross
B. Codominance
C. Testcross
D. Pedigree analysis
Correct Answer: B. Codominance
Explanation: Codominance is an allelic relationship in which both alleles are distinctly
expressed in the heterozygote. In this item, the key clue is that AB blood type expresses
both A and B antigens on red cells. A useful distinguishing feature is that codominance
differs from incomplete dominance because the two products remain individually
detectable rather than blending. The other choices describe related ideas, but they do not
match this full combination of definition, evidence, and distinguishing feature.
Question 4.
Which concept best accounts for both the observation that a prophage remains silent
through many bacterial divisions before induction and the fact that environmental stress
can trigger transition from lysogeny to productive lytic growth? Choose the most precise
course-level interpretation.
A. Replica plating
B. Lysogenic cycle
C. Transformation
D. Bacterial recombination
Correct Answer: B. Lysogenic cycle
Explanation: Lysogenic cycle is a phage state in which viral DNA integrates or persists in
the host and replicates with the bacterium without immediate lysis. In this item, the key
clue is that a prophage remains silent through many bacterial divisions before induction. A
useful distinguishing feature is that environmental stress can trigger transition from
lysogeny to productive lytic growth. The other choices describe related ideas, but they do
not match this full combination of definition, evidence, and distinguishing feature.
Question 5.
The finding that individuals with the same susceptibility allele show different outcomes
under different exposures is an example of which concept?
A. F1 generation
B. Genotype
C. Phenotype
D. Gene-environment interaction
Correct Answer: D. Gene-environment interaction
,Explanation: Gene-environment interaction is a situation in which the phenotypic effect
of a genotype depends on environmental conditions. In this item, the key clue is that
individuals with the same susceptibility allele show different outcomes under different
exposures. A useful distinguishing feature is that genetic influence does not mean a
phenotype is independent of environment. The other choices describe related ideas, but
they do not match this full combination of definition, evidence, and distinguishing feature.
Question 6.
A practical example involves a situation in which a tumor suppressor promoter becomes
heavily methylated and gene expression falls without a DNA-sequence mutation. Which
concept is being applied?
A. Proto-oncogene
B. Precision oncology
C. DNA methylation
D. Tumor suppressor gene
Correct Answer: C. DNA methylation
Explanation: DNA methylation is an epigenetic modification often associated with
reduced transcription when concentrated in gene regulatory CpG regions. In this item, the
key clue is that a tumor suppressor promoter becomes heavily methylated and gene
expression falls without a DNA-sequence mutation. A useful distinguishing feature is that
epigenetic silencing can contribute to cancer while remaining potentially reversible. The
other choices describe related ideas, but they do not match this full combination of
definition, evidence, and distinguishing feature.
Question 7.
A practical example involves a situation in which an individual carries A on one homolog
and a on the other. Which concept is being applied?
A. Genotype
B. Heterozygous genotype
C. Locus
D. F1 generation
Correct Answer: B. Heterozygous genotype
Explanation: Heterozygous genotype is a genotype containing two different alleles at a
locus in a diploid organism. In this item, the key clue is that an individual carries A on one
homolog and a on the other. A useful distinguishing feature is that under complete
dominance the dominant phenotype can conceal the recessive allele. The other choices
describe related ideas, but they do not match this full combination of definition, evidence,
and distinguishing feature.
, Question 8.
Which concept is most directly represented when a histidine-requiring bacterial strain
regains growth on histidine-free medium after exposure to a test chemical? Choose the
most precise course-level interpretation.
A. Chromosomal duplication
B. Chromosomal deletion
C. Silent mutation
D. Ames test
Correct Answer: D. Ames test
Explanation: Ames test is a bacterial assay used to screen chemicals for mutagenic
potential by measuring mutation-dependent reversion. In this item, the key clue is that a
histidine-requiring bacterial strain regains growth on histidine-free medium after exposure
to a test chemical. A useful distinguishing feature is that increased revertant colonies
suggest the chemical or a metabolite can induce mutations. The other choices describe
related ideas, but they do not match this full combination of definition, evidence, and
distinguishing feature.
Question 9.
Which concept should be selected for the observation that a single tRNA species can
decode several codons differing at the third base?
A. Transfer RNA
B. DNA helicase
C. Wobble base pairing
D. RNA polymerase
Correct Answer: C. Wobble base pairing
Explanation: Wobble base pairing is flexible pairing at the third codon position that
allows one tRNA to recognize more than one synonymous codon. In this item, the key clue
is that a single tRNA species can decode several codons differing at the third base. A
useful distinguishing feature is that wobble contributes to degeneracy of the genetic code
without altering the encoded amino acid. The other choices describe related ideas, but
they do not match this full combination of definition, evidence, and distinguishing feature.
Question 10.
Which concept best accounts for both the observation that a prophage remains silent
through many bacterial divisions before induction and the fact that environmental stress
can trigger transition from lysogeny to productive lytic growth?
A. Lysogenic cycle
B. Specialized transduction
C. Transduction
D. Horizontal gene transfer
Correct Answer: A. Lysogenic cycle
