BIOL 101 Week 6 Quiz V3 | BIOL 101 Principles of
Biology | Actual Q&A with Rationale (BIOL101
Week 6 Quiz) | Liberty University
1. In a standard Mendelian monohybrid cross between two heterozygous (Pp) pea plants,
what is the expected phenotypic ratio of the offspring in the F2 generation?
A. 1:1
B. 1:2:1
C. 9:3:3:1
D. 3:1
Correct Answer: D
Explanation: The 3:1 ratio represents the probability of the dominant phenotype
appearing compared to the recessive phenotype. This occurs because the alleles segregate
independently during gamete formation, leading to three combinations containing the
dominant allele and one homozygous recessive combination. This foundational principle
was established by Gregor Mendel through his observations of garden peas.
2. Which enzyme is responsible for unwinding the DNA double helix during the process of
replication?
A. DNA Polymerase
B. Ligase
,C. Helicase
D. RNA Primase
Correct Answer: C
Explanation: Helicase is the specific enzyme that breaks the hydrogen bonds between the
nitrogenous bases to separate the DNA strands. This action creates the replication fork,
which allows other enzymes access to the template strands. Without the action of helicase,
the double-stranded DNA would remain coiled and replication could not proceed.
3. Which of the following nitrogenous bases is found in RNA but not in DNA?
A. Thymine
B. Adenine
C. Guanine
D. Uracil
Correct Answer: D
Explanation: RNA uses uracil as a pyrimidine base that pairs with adenine, replacing the
thymine found in DNA. This chemical difference is one of the primary structural
distinctions between the two types of nucleic acids. Additionally, uracil is less stable than
thymine, which reflects the temporary nature of mRNA transcripts compared to the
permanent storage of DNA.
, 4. During DNA replication, what is the function of the enzyme DNA Ligase?
A. Adding new nucleotides to the leading strand
B. Synthesizing an RNA primer
C. Joining Okazaki fragments on the lagging strand
D. Proofreading the newly synthesized DNA
Correct Answer: C
Explanation: DNA Ligase acts as a molecular glue that seals the gaps between the sugar-
phosphate backbones of DNA fragments. It is particularly essential on the lagging strand,
where replication occurs in short, discontinuous segments called Okazaki fragments. This
enzymatic step ensures that the final DNA product is a continuous, unbroken strand.
5. An individual who possesses two different alleles for a specific gene is described as being:
A. Homozygous dominant
B. Hemizygous
C. Homozygous recessive
D. Heterozygous
Correct Answer: D
Explanation: Heterozygosity occurs when an organism inherits one dominant allele and
one recessive allele for a particular trait. In complete dominance scenarios, the phenotype
of a heterozygote will typically resemble the dominant trait. This genetic condition is
Biology | Actual Q&A with Rationale (BIOL101
Week 6 Quiz) | Liberty University
1. In a standard Mendelian monohybrid cross between two heterozygous (Pp) pea plants,
what is the expected phenotypic ratio of the offspring in the F2 generation?
A. 1:1
B. 1:2:1
C. 9:3:3:1
D. 3:1
Correct Answer: D
Explanation: The 3:1 ratio represents the probability of the dominant phenotype
appearing compared to the recessive phenotype. This occurs because the alleles segregate
independently during gamete formation, leading to three combinations containing the
dominant allele and one homozygous recessive combination. This foundational principle
was established by Gregor Mendel through his observations of garden peas.
2. Which enzyme is responsible for unwinding the DNA double helix during the process of
replication?
A. DNA Polymerase
B. Ligase
,C. Helicase
D. RNA Primase
Correct Answer: C
Explanation: Helicase is the specific enzyme that breaks the hydrogen bonds between the
nitrogenous bases to separate the DNA strands. This action creates the replication fork,
which allows other enzymes access to the template strands. Without the action of helicase,
the double-stranded DNA would remain coiled and replication could not proceed.
3. Which of the following nitrogenous bases is found in RNA but not in DNA?
A. Thymine
B. Adenine
C. Guanine
D. Uracil
Correct Answer: D
Explanation: RNA uses uracil as a pyrimidine base that pairs with adenine, replacing the
thymine found in DNA. This chemical difference is one of the primary structural
distinctions between the two types of nucleic acids. Additionally, uracil is less stable than
thymine, which reflects the temporary nature of mRNA transcripts compared to the
permanent storage of DNA.
, 4. During DNA replication, what is the function of the enzyme DNA Ligase?
A. Adding new nucleotides to the leading strand
B. Synthesizing an RNA primer
C. Joining Okazaki fragments on the lagging strand
D. Proofreading the newly synthesized DNA
Correct Answer: C
Explanation: DNA Ligase acts as a molecular glue that seals the gaps between the sugar-
phosphate backbones of DNA fragments. It is particularly essential on the lagging strand,
where replication occurs in short, discontinuous segments called Okazaki fragments. This
enzymatic step ensures that the final DNA product is a continuous, unbroken strand.
5. An individual who possesses two different alleles for a specific gene is described as being:
A. Homozygous dominant
B. Hemizygous
C. Homozygous recessive
D. Heterozygous
Correct Answer: D
Explanation: Heterozygosity occurs when an organism inherits one dominant allele and
one recessive allele for a particular trait. In complete dominance scenarios, the phenotype
of a heterozygote will typically resemble the dominant trait. This genetic condition is
