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BIO 210 FINAL EXAM — GENETICS
QUESTIONS WITH ANSWERS AND
RATIONALES 2026/2027
1. Which of the following best defines a gene?
A. A protein that determines a trait
B. A segment of DNA that codes for a functional product
C. A chromosome that carries multiple traits
D. A molecule of RNA that regulates metabolism
Correct Answer: B
Rationale: A gene is a segment of DNA that contains the instructions for making a
functional product, typically a protein or functional RNA.
2. In Mendel's experiments, the trait that disappeared in the F1 generation but
reappeared in the F2 generation was called:
A. Dominant
B. Recessive
C. Codominant
D. Epistatic
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Correct Answer: B
Rationale: Recessive traits are masked in the presence of a dominant allele in the
F1 generation but reappear in the F2 generation when two recessive alleles
combine.
3. What is the phenotypic ratio of a monohybrid cross between two heterozygous
individuals (Tt × Tt)?
A. 1:1
B. 3:1
C. 1:2:1
D. 9:3:3:1
Correct Answer: B
Rationale: A Tt × Tt cross produces a 3:1 phenotypic ratio (3 dominant : 1
recessive) and a 1:2:1 genotypic ratio.
4. Which of the following describes an organism with two identical alleles for a
trait?
A. Heterozygous
B. Homozygous
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C. Hemizygous
D. Hybrid
Correct Answer: B
Rationale: Homozygous describes an organism carrying two identical alleles (e.g.,
TT or tt) for a given gene.
5. The physical expression of a genotype is called the:
A. Genotype
B. Phenotype
C. Karyotype
D. Allele
Correct Answer: B
Rationale: Phenotype refers to the observable physical or biochemical
characteristics resulting from the genotype and environmental influences.
6. In a dihybrid cross (RrYy × RrYy), what is the expected phenotypic ratio?
A. 1:1:1:1
B. 3:1
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C. 9:3:3:1
D. 1:2:1
Correct Answer: C
Rationale: A dihybrid cross between two heterozygous individuals produces the
classic 9:3:3:1 phenotypic ratio when genes assort independently.
7. Mendel's law of independent assortment states that:
A. Alleles separate during gamete formation
B. Genes on different chromosomes assort independently during meiosis
C. Dominant alleles always mask recessive alleles
D. All traits are inherited together
Correct Answer: B
Rationale: The law of independent assortment states that alleles of different
genes segregate independently of one another during gamete formation when
the genes are on different chromosomes.
8. A testcross is performed to determine:
A. Whether an organism is homozygous dominant or heterozygous
B. The number of chromosomes in an organism
BIO 210 FINAL EXAM — GENETICS
QUESTIONS WITH ANSWERS AND
RATIONALES 2026/2027
1. Which of the following best defines a gene?
A. A protein that determines a trait
B. A segment of DNA that codes for a functional product
C. A chromosome that carries multiple traits
D. A molecule of RNA that regulates metabolism
Correct Answer: B
Rationale: A gene is a segment of DNA that contains the instructions for making a
functional product, typically a protein or functional RNA.
2. In Mendel's experiments, the trait that disappeared in the F1 generation but
reappeared in the F2 generation was called:
A. Dominant
B. Recessive
C. Codominant
D. Epistatic
,2|Page
Correct Answer: B
Rationale: Recessive traits are masked in the presence of a dominant allele in the
F1 generation but reappear in the F2 generation when two recessive alleles
combine.
3. What is the phenotypic ratio of a monohybrid cross between two heterozygous
individuals (Tt × Tt)?
A. 1:1
B. 3:1
C. 1:2:1
D. 9:3:3:1
Correct Answer: B
Rationale: A Tt × Tt cross produces a 3:1 phenotypic ratio (3 dominant : 1
recessive) and a 1:2:1 genotypic ratio.
4. Which of the following describes an organism with two identical alleles for a
trait?
A. Heterozygous
B. Homozygous
,3|Page
C. Hemizygous
D. Hybrid
Correct Answer: B
Rationale: Homozygous describes an organism carrying two identical alleles (e.g.,
TT or tt) for a given gene.
5. The physical expression of a genotype is called the:
A. Genotype
B. Phenotype
C. Karyotype
D. Allele
Correct Answer: B
Rationale: Phenotype refers to the observable physical or biochemical
characteristics resulting from the genotype and environmental influences.
6. In a dihybrid cross (RrYy × RrYy), what is the expected phenotypic ratio?
A. 1:1:1:1
B. 3:1
, 4|Page
C. 9:3:3:1
D. 1:2:1
Correct Answer: C
Rationale: A dihybrid cross between two heterozygous individuals produces the
classic 9:3:3:1 phenotypic ratio when genes assort independently.
7. Mendel's law of independent assortment states that:
A. Alleles separate during gamete formation
B. Genes on different chromosomes assort independently during meiosis
C. Dominant alleles always mask recessive alleles
D. All traits are inherited together
Correct Answer: B
Rationale: The law of independent assortment states that alleles of different
genes segregate independently of one another during gamete formation when
the genes are on different chromosomes.
8. A testcross is performed to determine:
A. Whether an organism is homozygous dominant or heterozygous
B. The number of chromosomes in an organism
