BIOD 210 Genetics - Module 6: Heredity, Complex Traits, and
Epigenetics Exam 2026/2027 UPDATE
1. Which of the following best defines a polygenic trait?
A. A trait controlled by the additive effect of multiple genes
B. A trait determined by a single gene with two alleles
C. A trait that is only expressed in one sex
D. A trait influenced solely by environmental factors
Answer: A
Rationale: Polygenic traits are controlled by two or more genes, typically having an
additive effect on the phenotype, resulting in continuous variation.
2. In genetics, what does the term ‘epigenetics’ refer to?
A. Changes in the DNA sequence through point mutations
B. The study of how environment influences the genetic code itself
C. The process of protein synthesis from an mRNA template
D. Heritable changes in gene expression that do not involve changes to the underlying DNA sequence
Answer: D
Rationale: Epigenetics involves modifications like DNA methylation or histone acetylation
that change how genes are expressed without altering the DNA sequence.
,3. Which type of twins share 100% of their genetic material?
A. Monozygotic (MZ) twins
B. Fraternal twins
C. Dizygotic (DZ) twins
D. Semi-identical twins
Answer: A
Rationale: Monozygotic twins come from a single fertilized egg that splits into two
embryos, sharing 100% of their DNA.
4. What is the primary effect of DNA methylation on gene expression?
A. It typically silences or reduces gene expression
B. It increases the rate of transcription
C. It changes the amino acid sequence of the protein
D. It removes introns from the pre-mRNA
Answer: A
Rationale: Methylation of CpG islands in promoter regions usually prevents transcription
factor binding, leading to gene silencing.
5. Broad-sense heritability (H²) is defined as:
A. The proportion of phenotypic variance due to environmental factors
B. The proportion of phenotypic variance due to additive genetic effects only
C. The likelihood that a trait will be passed to the next generation
D. The ratio of total genetic variance to total phenotypic variance
Answer: D
Rationale: Broad-sense heritability includes all genetic components (additive, dominance,
and epistasis) relative to the total phenotypic variance.
, 6. Which of the following is an example of a multifactorial trait?
A. Cystic Fibrosis
B. Human height
C. ABO blood type
D. Huntington’s disease
Answer: B
Rationale: Height is influenced by both multiple genes (polygenic) and environmental
factors such as nutrition, making it multifactorial.
7. What does a concordance rate of 100% in monozygotic twins and 50% in
dizygotic twins suggest for a trait?
A. The trait is entirely determined by the environment
B. The trait has a strong genetic component
C. The trait is X-linked recessive
D. The trait is not heritable
Answer: B
Rationale: If MZ twins are much more similar than DZ twins, it indicates that genes play a
significant role in the phenotype.
8. Histone acetylation generally results in:
A. Relaxed chromatin structure and increased transcription
B. Tighter packing of chromatin and gene silencing
C. The degradation of the histone protein
D. The permanent removal of the gene from the chromosome
Answer: A
Rationale: Acetylation neutralizes the positive charge of histones, loosening their grip on
DNA and allowing transcription machinery to access genes.
Epigenetics Exam 2026/2027 UPDATE
1. Which of the following best defines a polygenic trait?
A. A trait controlled by the additive effect of multiple genes
B. A trait determined by a single gene with two alleles
C. A trait that is only expressed in one sex
D. A trait influenced solely by environmental factors
Answer: A
Rationale: Polygenic traits are controlled by two or more genes, typically having an
additive effect on the phenotype, resulting in continuous variation.
2. In genetics, what does the term ‘epigenetics’ refer to?
A. Changes in the DNA sequence through point mutations
B. The study of how environment influences the genetic code itself
C. The process of protein synthesis from an mRNA template
D. Heritable changes in gene expression that do not involve changes to the underlying DNA sequence
Answer: D
Rationale: Epigenetics involves modifications like DNA methylation or histone acetylation
that change how genes are expressed without altering the DNA sequence.
,3. Which type of twins share 100% of their genetic material?
A. Monozygotic (MZ) twins
B. Fraternal twins
C. Dizygotic (DZ) twins
D. Semi-identical twins
Answer: A
Rationale: Monozygotic twins come from a single fertilized egg that splits into two
embryos, sharing 100% of their DNA.
4. What is the primary effect of DNA methylation on gene expression?
A. It typically silences or reduces gene expression
B. It increases the rate of transcription
C. It changes the amino acid sequence of the protein
D. It removes introns from the pre-mRNA
Answer: A
Rationale: Methylation of CpG islands in promoter regions usually prevents transcription
factor binding, leading to gene silencing.
5. Broad-sense heritability (H²) is defined as:
A. The proportion of phenotypic variance due to environmental factors
B. The proportion of phenotypic variance due to additive genetic effects only
C. The likelihood that a trait will be passed to the next generation
D. The ratio of total genetic variance to total phenotypic variance
Answer: D
Rationale: Broad-sense heritability includes all genetic components (additive, dominance,
and epistasis) relative to the total phenotypic variance.
, 6. Which of the following is an example of a multifactorial trait?
A. Cystic Fibrosis
B. Human height
C. ABO blood type
D. Huntington’s disease
Answer: B
Rationale: Height is influenced by both multiple genes (polygenic) and environmental
factors such as nutrition, making it multifactorial.
7. What does a concordance rate of 100% in monozygotic twins and 50% in
dizygotic twins suggest for a trait?
A. The trait is entirely determined by the environment
B. The trait has a strong genetic component
C. The trait is X-linked recessive
D. The trait is not heritable
Answer: B
Rationale: If MZ twins are much more similar than DZ twins, it indicates that genes play a
significant role in the phenotype.
8. Histone acetylation generally results in:
A. Relaxed chromatin structure and increased transcription
B. Tighter packing of chromatin and gene silencing
C. The degradation of the histone protein
D. The permanent removal of the gene from the chromosome
Answer: A
Rationale: Acetylation neutralizes the positive charge of histones, loosening their grip on
DNA and allowing transcription machinery to access genes.
