BIOL 101 Week 6 Quiz V2 | BIOL 101 Principles of
Biology | Actual Q&A with Rationale (BIOL101
Week 6 Quiz) | Liberty University
1. Which enzyme is responsible for unwinding the DNA double helix during the replication
process?
A. DNA Polymerase
B. DNA Ligase
C. Helicase
D. RNA Primase
Correct Answer: C
Explanation: Helicase functions by breaking the hydrogen bonds between the nitrogenous
bases of the DNA strands. This action creates a replication fork which allows other enzymes
to access the single-stranded templates. Without helicase, the double-stranded DNA would
remain coiled and inaccessible for duplication.
2. In Mendelian genetics, what term describes an organism that has two different alleles for a
specific trait?
A. Homozygous dominant
B. Hemizygous
C. Homozygous recessive
,D. Heterozygous
Correct Answer: D
Explanation: An individual is considered heterozygous when they inherit one dominant
allele and one recessive allele for a gene. This condition often results in the expression of
the dominant phenotype while the recessive trait remains hidden. This fundamental
concept explains how genetic diversity is maintained within a population’s gene pool.
3. During which phase of protein synthesis is a ribosome moving along an mRNA strand to
read codons?
A. Transcription
B. Replication
C. Translation
D. Transformation
Correct Answer: C
Explanation: Translation occurs in the cytoplasm where the ribosome decodes the mRNA
sequence into a polypeptide chain. This process involves tRNA molecules bringing specific
amino acids that correspond to the mRNA codons. It is the final step of the central dogma
where genetic information is expressed as a functional protein.
4. Which of the following nitrogenous bases is found in RNA but not in DNA?
A. Adenine
, B. Thymine
C. Guanine
D. Uracil
Correct Answer: D
Explanation: RNA uses uracil as a pyrimidine base which pairs with adenine instead of the
thymine found in DNA. The presence of uracil is one of the primary chemical differences
that distinguishes RNA from its deoxyribose counterpart. This substitution is critical for the
cell to recognize and handle different types of nucleic acids appropriately.
5. What is the expected phenotypic ratio of a cross between two individuals heterozygous for
a single trait (Bb x Bb)?
A. 1:1
B. 1:2:1
C. 3:1
D. 9:3:3:1
Correct Answer: C
Explanation: A monohybrid cross between two heterozygotes typically yields a 3:1 ratio of
dominant to recessive phenotypes. While the genotypic ratio is 1:2:1, the dominant allele
masks the recessive one in three out of four offspring. This ratio was one of the key findings
in Gregor Mendel’s classic experiments with pea plants.
Biology | Actual Q&A with Rationale (BIOL101
Week 6 Quiz) | Liberty University
1. Which enzyme is responsible for unwinding the DNA double helix during the replication
process?
A. DNA Polymerase
B. DNA Ligase
C. Helicase
D. RNA Primase
Correct Answer: C
Explanation: Helicase functions by breaking the hydrogen bonds between the nitrogenous
bases of the DNA strands. This action creates a replication fork which allows other enzymes
to access the single-stranded templates. Without helicase, the double-stranded DNA would
remain coiled and inaccessible for duplication.
2. In Mendelian genetics, what term describes an organism that has two different alleles for a
specific trait?
A. Homozygous dominant
B. Hemizygous
C. Homozygous recessive
,D. Heterozygous
Correct Answer: D
Explanation: An individual is considered heterozygous when they inherit one dominant
allele and one recessive allele for a gene. This condition often results in the expression of
the dominant phenotype while the recessive trait remains hidden. This fundamental
concept explains how genetic diversity is maintained within a population’s gene pool.
3. During which phase of protein synthesis is a ribosome moving along an mRNA strand to
read codons?
A. Transcription
B. Replication
C. Translation
D. Transformation
Correct Answer: C
Explanation: Translation occurs in the cytoplasm where the ribosome decodes the mRNA
sequence into a polypeptide chain. This process involves tRNA molecules bringing specific
amino acids that correspond to the mRNA codons. It is the final step of the central dogma
where genetic information is expressed as a functional protein.
4. Which of the following nitrogenous bases is found in RNA but not in DNA?
A. Adenine
, B. Thymine
C. Guanine
D. Uracil
Correct Answer: D
Explanation: RNA uses uracil as a pyrimidine base which pairs with adenine instead of the
thymine found in DNA. The presence of uracil is one of the primary chemical differences
that distinguishes RNA from its deoxyribose counterpart. This substitution is critical for the
cell to recognize and handle different types of nucleic acids appropriately.
5. What is the expected phenotypic ratio of a cross between two individuals heterozygous for
a single trait (Bb x Bb)?
A. 1:1
B. 1:2:1
C. 3:1
D. 9:3:3:1
Correct Answer: C
Explanation: A monohybrid cross between two heterozygotes typically yields a 3:1 ratio of
dominant to recessive phenotypes. While the genotypic ratio is 1:2:1, the dominant allele
masks the recessive one in three out of four offspring. This ratio was one of the key findings
in Gregor Mendel’s classic experiments with pea plants.
