BIOL180 Lesson 6 Quiz – Mendelian
Genetics Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
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1. In pea plants, purple flower color (P) is dominant over white flower
color (p). What is the expected phenotypic ratio from a cross between
two heterozygous purple-flowered plants (Pp × Pp)?
A. 1 purple : 3 white
B. 3 purple : 1 white
C. 1 purple : 1 white
D. All purple
Rationale: Crossing two heterozygous individuals produces the genotypes
PP, Pp, Pp, and pp. Three offspring have purple flowers, while one has
white flowers, giving a 3:1 phenotypic ratio.
2. Which Mendelian principle states that the two alleles for a trait
separate during gamete formation?
A. Law of Independent Assortment
B. Law of Dominance
C. Law of Segregation
D. Law of Variation
,Rationale: The Law of Segregation states that paired alleles separate
during meiosis so each gamete receives only one allele for each gene.
3. A pea plant with genotype TT is crossed with a pea plant having
genotype tt. What will be the genotype of all F₁ offspring?
A. TT
B. tt
C. Tt
D. 50% TT and 50% tt
Rationale: Every offspring receives one dominant T allele from one parent
and one recessive t allele from the other, making all offspring heterozygous
Tt.
4. What is the probability that a heterozygous × heterozygous cross (Aa ×
Aa) will produce a homozygous recessive offspring?
A. 1/2
B. 3/4
C. 1/4
D. 0
Rationale: The Punnett square yields AA, Aa, Aa, and aa. Only one of the
four possible genotypes is homozygous recessive.
5. Which genotype represents a homozygous dominant individual?
A. Aa
B. aa
C. AA
D. Aa and aa
Rationale: Homozygous dominant means both alleles are dominant,
represented by two uppercase letters.
6. In Mendel's experiments, what term describes the observable
characteristic of an organism?
, A. Genotype
B. Allele
C. Phenotype
D. Locus
Rationale: A phenotype is the physical or observable expression of a trait,
such as flower color or seed shape.
7. Which genotype is heterozygous?
A. AA
B. aa
C. Aa
D. Both AA and aa
Rationale: A heterozygous genotype contains two different alleles for a
particular gene.
8. What is the expected genotypic ratio from a monohybrid cross
between two heterozygous individuals (Aa × Aa)?
A. 3:1
B. 1:2:1
C. 1:1
D. 9:3:3:1
Rationale: The resulting genotypes are AA, Aa, Aa, and aa, giving a ratio of
1:2:1.
9. Which of the following best defines an allele?
A. A chromosome
B. A protein
C. An alternative form of a gene
D. A type of cell
Rationale: Alleles are different versions of the same gene that occupy the
same location on homologous chromosomes.
Genetics Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
1. In pea plants, purple flower color (P) is dominant over white flower
color (p). What is the expected phenotypic ratio from a cross between
two heterozygous purple-flowered plants (Pp × Pp)?
A. 1 purple : 3 white
B. 3 purple : 1 white
C. 1 purple : 1 white
D. All purple
Rationale: Crossing two heterozygous individuals produces the genotypes
PP, Pp, Pp, and pp. Three offspring have purple flowers, while one has
white flowers, giving a 3:1 phenotypic ratio.
2. Which Mendelian principle states that the two alleles for a trait
separate during gamete formation?
A. Law of Independent Assortment
B. Law of Dominance
C. Law of Segregation
D. Law of Variation
,Rationale: The Law of Segregation states that paired alleles separate
during meiosis so each gamete receives only one allele for each gene.
3. A pea plant with genotype TT is crossed with a pea plant having
genotype tt. What will be the genotype of all F₁ offspring?
A. TT
B. tt
C. Tt
D. 50% TT and 50% tt
Rationale: Every offspring receives one dominant T allele from one parent
and one recessive t allele from the other, making all offspring heterozygous
Tt.
4. What is the probability that a heterozygous × heterozygous cross (Aa ×
Aa) will produce a homozygous recessive offspring?
A. 1/2
B. 3/4
C. 1/4
D. 0
Rationale: The Punnett square yields AA, Aa, Aa, and aa. Only one of the
four possible genotypes is homozygous recessive.
5. Which genotype represents a homozygous dominant individual?
A. Aa
B. aa
C. AA
D. Aa and aa
Rationale: Homozygous dominant means both alleles are dominant,
represented by two uppercase letters.
6. In Mendel's experiments, what term describes the observable
characteristic of an organism?
, A. Genotype
B. Allele
C. Phenotype
D. Locus
Rationale: A phenotype is the physical or observable expression of a trait,
such as flower color or seed shape.
7. Which genotype is heterozygous?
A. AA
B. aa
C. Aa
D. Both AA and aa
Rationale: A heterozygous genotype contains two different alleles for a
particular gene.
8. What is the expected genotypic ratio from a monohybrid cross
between two heterozygous individuals (Aa × Aa)?
A. 3:1
B. 1:2:1
C. 1:1
D. 9:3:3:1
Rationale: The resulting genotypes are AA, Aa, Aa, and aa, giving a ratio of
1:2:1.
9. Which of the following best defines an allele?
A. A chromosome
B. A protein
C. An alternative form of a gene
D. A type of cell
Rationale: Alleles are different versions of the same gene that occupy the
same location on homologous chromosomes.
