BIOL 210 Module 3: Non-Mendelian Inheritance
and Genetic Diversity Updated and Latest
Questions and Correct Answers with Rationale
1. Which inheritance pattern is characterized by a heterozygous phenotype that is an
intermediate blend of the two homozygous phenotypes?
A. Incomplete dominance
B. Codominance
C. Epistasis
D. Polygenic inheritance
Correct Answer: A
Explanation: Incomplete dominance occurs when the dominant allele does not completely
mask the recessive allele, resulting in a blended phenotype. Codominance shows both
alleles equally, while polygenic involves multiple genes.
2. In the ABO blood group system, which alleles are codominant with each other?
A. A and O
B. A and B
C. B and O
D. All three alleles
Correct Answer: B
Explanation: Alleles A and B are both expressed fully when present together, making them
codominant. The O allele is recessive to both A and B.
3. Human skin color is influenced by several different genes. This is an example of what type
of inheritance?
A. Multiple alleles
B. Polygenic inheritance
C. Pleiotropy
D. Incomplete dominance
Correct Answer: B
Explanation: Polygenic inheritance occurs when one trait is controlled by multiple genes,
often leading to a wide range of phenotypic variation like skin tone or height.
,4. A cross between a red-flowered snapdragon and a white-flowered snapdragon produces all
pink offspring. If these pink offspring are self-pollinated, what is the expected phenotypic
ratio of the F2 generation?
A. 3 red : 1 white
B. 9 red : 3 pink : 4 white
C. 1 red : 2 pink : 1 white
D. All pink
Correct Answer: C
Explanation: For incomplete dominance, the F2 ratio for both genotype and phenotype is
1:2:1 (1 homozygous dominant, 2 heterozygous, 1 homozygous recessive).
5. A woman with type AB blood and a man with type O blood have children. What are the
possible blood types of their children?
A. Only AB and O
B. A, B, and AB
C. Only A and B
D. A, B, AB, and O
Correct Answer: C
Explanation: The woman (AB) provides either an A or B allele. The man (OO) provides
only O. The combinations AO and BO result in Type A and Type B phenotypes.
6. Which term describes the situation where a single gene has multiple effects on an
individual’s phenotype?
A. Polygenic inheritance
B. Codominance
C. Epistasis
D. Pleiotropy
Correct Answer: D
Explanation: Pleiotropy refers to one gene influencing multiple seemingly unrelated
phenotypic traits, such as Marfan syndrome affecting the heart and the skeleton.
7. If a black chicken (BB) is crossed with a white chicken (WW) and the resulting offspring are
all speckled (BW) with both black and white feathers, what inheritance pattern is displayed?
A. Codominance
B. Incomplete dominance
, C. Multiple alleles
D. Epistasis
Correct Answer: A
Explanation: In codominance, both alleles are expressed distinctly in the heterozygote. A
speckled pattern shows both black and white, not a gray blend.
8. In mice, one gene determines the color of the fur, but a second gene determines whether
or not any pigment is deposited at all. This interaction is called:
A. Codominance
B. Pleiotropy
C. Epistasis
D. Polygenic inheritance
Correct Answer: C
Explanation: Epistasis occurs when the expression of one gene (pigment deposition)
masks or modifies the expression of another gene (fur color).
9. What is the primary characteristic of traits that follow a polygenic inheritance pattern?
A. They show continuous variation in a population.
B. They are usually located on the X chromosome.
C. They show discrete, ‘either-or’ phenotypes.
D. They are only expressed in males.
Correct Answer: A
Explanation: Because multiple genes contribute to the phenotype, polygenic traits
typically result in a bell-shaped curve of variation rather than distinct categories.
10. Which of the following is an example of a trait controlled by multiple alleles in humans?
A. ABO blood group
B. Height
C. Color blindness
D. Attached earlobes
Correct Answer: A
Explanation: The ABO blood group system involves three alleles (A, B, and O) within the
population, although an individual only carries two.
and Genetic Diversity Updated and Latest
Questions and Correct Answers with Rationale
1. Which inheritance pattern is characterized by a heterozygous phenotype that is an
intermediate blend of the two homozygous phenotypes?
A. Incomplete dominance
B. Codominance
C. Epistasis
D. Polygenic inheritance
Correct Answer: A
Explanation: Incomplete dominance occurs when the dominant allele does not completely
mask the recessive allele, resulting in a blended phenotype. Codominance shows both
alleles equally, while polygenic involves multiple genes.
2. In the ABO blood group system, which alleles are codominant with each other?
A. A and O
B. A and B
C. B and O
D. All three alleles
Correct Answer: B
Explanation: Alleles A and B are both expressed fully when present together, making them
codominant. The O allele is recessive to both A and B.
3. Human skin color is influenced by several different genes. This is an example of what type
of inheritance?
A. Multiple alleles
B. Polygenic inheritance
C. Pleiotropy
D. Incomplete dominance
Correct Answer: B
Explanation: Polygenic inheritance occurs when one trait is controlled by multiple genes,
often leading to a wide range of phenotypic variation like skin tone or height.
,4. A cross between a red-flowered snapdragon and a white-flowered snapdragon produces all
pink offspring. If these pink offspring are self-pollinated, what is the expected phenotypic
ratio of the F2 generation?
A. 3 red : 1 white
B. 9 red : 3 pink : 4 white
C. 1 red : 2 pink : 1 white
D. All pink
Correct Answer: C
Explanation: For incomplete dominance, the F2 ratio for both genotype and phenotype is
1:2:1 (1 homozygous dominant, 2 heterozygous, 1 homozygous recessive).
5. A woman with type AB blood and a man with type O blood have children. What are the
possible blood types of their children?
A. Only AB and O
B. A, B, and AB
C. Only A and B
D. A, B, AB, and O
Correct Answer: C
Explanation: The woman (AB) provides either an A or B allele. The man (OO) provides
only O. The combinations AO and BO result in Type A and Type B phenotypes.
6. Which term describes the situation where a single gene has multiple effects on an
individual’s phenotype?
A. Polygenic inheritance
B. Codominance
C. Epistasis
D. Pleiotropy
Correct Answer: D
Explanation: Pleiotropy refers to one gene influencing multiple seemingly unrelated
phenotypic traits, such as Marfan syndrome affecting the heart and the skeleton.
7. If a black chicken (BB) is crossed with a white chicken (WW) and the resulting offspring are
all speckled (BW) with both black and white feathers, what inheritance pattern is displayed?
A. Codominance
B. Incomplete dominance
, C. Multiple alleles
D. Epistasis
Correct Answer: A
Explanation: In codominance, both alleles are expressed distinctly in the heterozygote. A
speckled pattern shows both black and white, not a gray blend.
8. In mice, one gene determines the color of the fur, but a second gene determines whether
or not any pigment is deposited at all. This interaction is called:
A. Codominance
B. Pleiotropy
C. Epistasis
D. Polygenic inheritance
Correct Answer: C
Explanation: Epistasis occurs when the expression of one gene (pigment deposition)
masks or modifies the expression of another gene (fur color).
9. What is the primary characteristic of traits that follow a polygenic inheritance pattern?
A. They show continuous variation in a population.
B. They are usually located on the X chromosome.
C. They show discrete, ‘either-or’ phenotypes.
D. They are only expressed in males.
Correct Answer: A
Explanation: Because multiple genes contribute to the phenotype, polygenic traits
typically result in a bell-shaped curve of variation rather than distinct categories.
10. Which of the following is an example of a trait controlled by multiple alleles in humans?
A. ABO blood group
B. Height
C. Color blindness
D. Attached earlobes
Correct Answer: A
Explanation: The ABO blood group system involves three alleles (A, B, and O) within the
population, although an individual only carries two.
