BIOL 101 Quiz 4 V3 | BIOL 101 Principles of
Biology | Actual Q&A with Rationale (BIOL101 Quiz
4) | Liberty University
1. During which phase of the cell cycle is DNA actually replicated?
A. S phase
B. G1 phase
C. G2 phase
D. M phase
Correct Answer: A
Explanation: The S phase, or synthesis phase, is the specific period during interphase
when the cell duplicates its genomic DNA. This ensures that when the cell eventually
divides, each daughter cell receives a complete and identical set of genetic information. The
G1 and G2 phases are primarily for growth and preparation, while the M phase involves the
physical division of the nucleus and cytoplasm.
2. Which enzyme is responsible for ‘unzipping’ the DNA double helix by breaking hydrogen
bonds between base pairs?
A. DNA Polymerase
B. Helicase
C. DNA Ligase
,D. Primase
Correct Answer: B
Explanation: Helicase is an essential enzyme that moves along the DNA molecule to
separate the two strands, creating a replication fork. By breaking the hydrogen bonds
between the nitrogenous bases, it allows other enzymes to access the single strands for
copying. Without helicase activity, the double-stranded DNA would remain coiled and
inaccessible for replication.
3. In Mendelian genetics, an organism that has two different alleles for a specific trait is
described as:
A. Homozygous dominant
B. Homozygous recessive
C. Hemizygous
D. Heterozygous
Correct Answer: D
Explanation: A heterozygous individual possesses one dominant allele and one recessive
allele for a particular gene locus. This combination often results in the dominant phenotype
being expressed while the recessive trait remains hidden. This condition contrasts with
homozygous states where both alleles for a gene are identical.
4. What is the primary product of the process of transcription?
A. A polypeptide chain
, B. An mRNA molecule
C. A new DNA molecule
D. A ribosome
Correct Answer: B
Explanation: Transcription is the first step of gene expression where a specific segment of
DNA is used as a template to synthesize messenger RNA (mRNA). This mRNA serves as a
portable copy of the genetic code that can leave the nucleus and travel to the ribosome. It
acts as the intermediary between the stored genetic information in the DNA and the
functional protein products.
5. During which specific stage of Meiosis I does crossing over occur between homologous
chromosomes?
A. Anaphase I
B. Metaphase I
C. Prophase I
D. Telophase I
Correct Answer: C
Explanation: Crossing over happens during Prophase I, where homologous chromosomes
pair up and exchange segments of their genetic material. This process is crucial because it
creates new combinations of alleles, increasing the genetic diversity of the resulting
Biology | Actual Q&A with Rationale (BIOL101 Quiz
4) | Liberty University
1. During which phase of the cell cycle is DNA actually replicated?
A. S phase
B. G1 phase
C. G2 phase
D. M phase
Correct Answer: A
Explanation: The S phase, or synthesis phase, is the specific period during interphase
when the cell duplicates its genomic DNA. This ensures that when the cell eventually
divides, each daughter cell receives a complete and identical set of genetic information. The
G1 and G2 phases are primarily for growth and preparation, while the M phase involves the
physical division of the nucleus and cytoplasm.
2. Which enzyme is responsible for ‘unzipping’ the DNA double helix by breaking hydrogen
bonds between base pairs?
A. DNA Polymerase
B. Helicase
C. DNA Ligase
,D. Primase
Correct Answer: B
Explanation: Helicase is an essential enzyme that moves along the DNA molecule to
separate the two strands, creating a replication fork. By breaking the hydrogen bonds
between the nitrogenous bases, it allows other enzymes to access the single strands for
copying. Without helicase activity, the double-stranded DNA would remain coiled and
inaccessible for replication.
3. In Mendelian genetics, an organism that has two different alleles for a specific trait is
described as:
A. Homozygous dominant
B. Homozygous recessive
C. Hemizygous
D. Heterozygous
Correct Answer: D
Explanation: A heterozygous individual possesses one dominant allele and one recessive
allele for a particular gene locus. This combination often results in the dominant phenotype
being expressed while the recessive trait remains hidden. This condition contrasts with
homozygous states where both alleles for a gene are identical.
4. What is the primary product of the process of transcription?
A. A polypeptide chain
, B. An mRNA molecule
C. A new DNA molecule
D. A ribosome
Correct Answer: B
Explanation: Transcription is the first step of gene expression where a specific segment of
DNA is used as a template to synthesize messenger RNA (mRNA). This mRNA serves as a
portable copy of the genetic code that can leave the nucleus and travel to the ribosome. It
acts as the intermediary between the stored genetic information in the DNA and the
functional protein products.
5. During which specific stage of Meiosis I does crossing over occur between homologous
chromosomes?
A. Anaphase I
B. Metaphase I
C. Prophase I
D. Telophase I
Correct Answer: C
Explanation: Crossing over happens during Prophase I, where homologous chromosomes
pair up and exchange segments of their genetic material. This process is crucial because it
creates new combinations of alleles, increasing the genetic diversity of the resulting
