BIOD 102 / BIOD102 — ESSENTIAL BIOLOGY II
WITH LAB DNA REPLICATION, PROTEIN
SYNTHESIS, GENE EXPRESSION & REGULATION,
DNA REPAIR, POST-TRANSCRIPTIONAL/POST-
TRANSLATIONAL MODIFICATION, TELOMERES &
MICROARRAY ANALYSIS100 ORIGINAL EXAM-
PREPARATION MULTIPLE-CHOICE QUESTIONS,
CORRECT ANSWERS & DETAILED RATIONALES
SECTION I — CELL CYCLE, DNA ORGANIZATION & REPLICATION FOUNDATIONS
Questions 1–15
1. During which phase of the cell cycle is nuclear DNA replicated?
A. S phase
B. G1 phase
C. G2 phase
D. M phase
Correct Answer: S phase
DNA replication occurs during the S, or synthesis, phase of interphase. During this stage,
each chromosome is copied so that duplicated genetic material is available for distribution
during cell division. G1 and G2 primarily involve growth and preparation, whereas M phase
involves chromosome segregation and cell division.
2. Which statement best describes the relationship between DNA replication and cell
division?
A. DNA replication occurs after cytokinesis.
B. DNA must be replicated before a dividing cell can distribute complete genetic information
to daughter cells.
C. DNA replication occurs only after chromosomes separate.
,D. DNA replication replaces mitosis.
Correct Answer: DNA must be replicated before a dividing cell can distribute complete
genetic information to daughter cells.
Replication produces a copy of the cell's genetic information before chromosome segregation
occurs. This allows daughter cells to receive the necessary genetic material. If replication
does not occur correctly, chromosome distribution can produce cells with incomplete or
abnormal genomes.
3. What does semiconservative replication mean?
A. Only one-half of the genome is replicated.
B. DNA is copied only during mitosis.
C. Each daughter DNA molecule contains one parental strand and one newly synthesized
strand.
D. Only the coding strand is copied.
Correct Answer: Each daughter DNA molecule contains one parental strand and one newly
synthesized strand.
Semiconservative replication preserves one original strand in each daughter DNA molecule.
Each parental strand serves as a template for synthesis of a complementary new strand. This
arrangement provides a reliable mechanism for preserving and transmitting genetic
information.
4. Which enzyme initially separates the two strands of DNA at a replication fork?
A. DNA ligase
B. Primase
C. DNA polymerase
D. Helicase
Correct Answer: Helicase
Helicase unwinds the DNA double helix by disrupting the hydrogen bonds between
complementary bases. This creates single-stranded templates that can be copied by DNA
polymerase. The other enzymes perform different functions during replication.
5. What is the primary function of single-stranded binding proteins during DNA
replication?
A. They stabilize separated DNA strands and prevent them from reannealing.
B. They synthesize RNA primers.
,C. They join Okazaki fragments.
D. They add amino acids to proteins.
Correct Answer: They stabilize separated DNA strands and prevent them from reannealing.
Once helicase separates DNA strands, single-stranded binding proteins associate with the
exposed strands. They stabilize the templates and help keep the strands separated. This
permits replication enzymes to access the DNA efficiently.
6. What is the main function of topoisomerase during DNA replication?
A. It adds amino acids to a polypeptide.
B. It relieves torsional stress created by DNA unwinding.
C. It removes introns.
D. It synthesizes the mRNA cap.
Correct Answer: It relieves torsional stress created by DNA unwinding.
Unwinding the DNA double helix produces twisting and tension ahead of the replication fork.
Topoisomerase reduces this stress by temporarily cutting and resealing DNA strands. This
allows replication to continue without excessive mechanical strain.
7. What is an origin of replication?
A. A protein that terminates translation
B. A section of RNA containing a codon
C. A DNA region where replication begins
D. The end of a chromosome
Correct Answer: A DNA region where replication begins
Replication begins at specific DNA locations called origins of replication. Proteins assemble at
these sites and establish replication machinery. Eukaryotic chromosomes generally contain
multiple origins because their genomes are large and require efficient duplication.
8. Why can DNA replication proceed from multiple origins in a eukaryotic chromosome?
A. Multiple origins allow large chromosomes to be copied more efficiently.
B. Multiple origins prevent transcription.
C. Each origin produces a different genetic code.
D. Multiple origins eliminate the need for DNA polymerase.
Correct Answer: Multiple origins allow large chromosomes to be copied more efficiently.
, Large eukaryotic chromosomes would take too long to replicate from a single starting point.
Multiple origins allow replication forks to operate simultaneously at different chromosome
locations. This greatly reduces the time required to duplicate the genome.
9. In what direction does DNA polymerase synthesize a new DNA strand?
A. 3′ to 5′
B. 5′ to 5′
C. 3′ to 3′
D. 5′ to 3′
Correct Answer: 5′ to 3′
DNA polymerase adds nucleotides to the free 3′ hydroxyl group of the growing strand.
Consequently, the new strand is always synthesized in the 5′ to 3′ direction. This directional
requirement explains why leading and lagging strands are synthesized differently.
10. Why is an RNA primer necessary during DNA replication?
A. It provides a starting point with a free 3′ hydroxyl group for DNA polymerase.
B. It terminates replication.
C. It prevents DNA from unwinding.
D. It replaces the entire DNA template.
Correct Answer: It provides a starting point with a free 3′ hydroxyl group for DNA
polymerase.
DNA polymerase cannot initiate a completely new strand without an existing nucleotide
chain. Primase synthesizes a short RNA primer that provides the necessary 3′ hydroxyl group.
DNA polymerase then extends the primer using DNA nucleotides.
11. Which enzyme synthesizes the RNA primer used during DNA replication?
A. Helicase
B. Primase
C. Ligase
D. Topoisomerase
Correct Answer: Primase
Primase synthesizes short RNA primers complementary to the DNA template. These primers
provide the starting points required by DNA polymerase. After replication, the RNA primers
are removed and replaced with DNA.
WITH LAB DNA REPLICATION, PROTEIN
SYNTHESIS, GENE EXPRESSION & REGULATION,
DNA REPAIR, POST-TRANSCRIPTIONAL/POST-
TRANSLATIONAL MODIFICATION, TELOMERES &
MICROARRAY ANALYSIS100 ORIGINAL EXAM-
PREPARATION MULTIPLE-CHOICE QUESTIONS,
CORRECT ANSWERS & DETAILED RATIONALES
SECTION I — CELL CYCLE, DNA ORGANIZATION & REPLICATION FOUNDATIONS
Questions 1–15
1. During which phase of the cell cycle is nuclear DNA replicated?
A. S phase
B. G1 phase
C. G2 phase
D. M phase
Correct Answer: S phase
DNA replication occurs during the S, or synthesis, phase of interphase. During this stage,
each chromosome is copied so that duplicated genetic material is available for distribution
during cell division. G1 and G2 primarily involve growth and preparation, whereas M phase
involves chromosome segregation and cell division.
2. Which statement best describes the relationship between DNA replication and cell
division?
A. DNA replication occurs after cytokinesis.
B. DNA must be replicated before a dividing cell can distribute complete genetic information
to daughter cells.
C. DNA replication occurs only after chromosomes separate.
,D. DNA replication replaces mitosis.
Correct Answer: DNA must be replicated before a dividing cell can distribute complete
genetic information to daughter cells.
Replication produces a copy of the cell's genetic information before chromosome segregation
occurs. This allows daughter cells to receive the necessary genetic material. If replication
does not occur correctly, chromosome distribution can produce cells with incomplete or
abnormal genomes.
3. What does semiconservative replication mean?
A. Only one-half of the genome is replicated.
B. DNA is copied only during mitosis.
C. Each daughter DNA molecule contains one parental strand and one newly synthesized
strand.
D. Only the coding strand is copied.
Correct Answer: Each daughter DNA molecule contains one parental strand and one newly
synthesized strand.
Semiconservative replication preserves one original strand in each daughter DNA molecule.
Each parental strand serves as a template for synthesis of a complementary new strand. This
arrangement provides a reliable mechanism for preserving and transmitting genetic
information.
4. Which enzyme initially separates the two strands of DNA at a replication fork?
A. DNA ligase
B. Primase
C. DNA polymerase
D. Helicase
Correct Answer: Helicase
Helicase unwinds the DNA double helix by disrupting the hydrogen bonds between
complementary bases. This creates single-stranded templates that can be copied by DNA
polymerase. The other enzymes perform different functions during replication.
5. What is the primary function of single-stranded binding proteins during DNA
replication?
A. They stabilize separated DNA strands and prevent them from reannealing.
B. They synthesize RNA primers.
,C. They join Okazaki fragments.
D. They add amino acids to proteins.
Correct Answer: They stabilize separated DNA strands and prevent them from reannealing.
Once helicase separates DNA strands, single-stranded binding proteins associate with the
exposed strands. They stabilize the templates and help keep the strands separated. This
permits replication enzymes to access the DNA efficiently.
6. What is the main function of topoisomerase during DNA replication?
A. It adds amino acids to a polypeptide.
B. It relieves torsional stress created by DNA unwinding.
C. It removes introns.
D. It synthesizes the mRNA cap.
Correct Answer: It relieves torsional stress created by DNA unwinding.
Unwinding the DNA double helix produces twisting and tension ahead of the replication fork.
Topoisomerase reduces this stress by temporarily cutting and resealing DNA strands. This
allows replication to continue without excessive mechanical strain.
7. What is an origin of replication?
A. A protein that terminates translation
B. A section of RNA containing a codon
C. A DNA region where replication begins
D. The end of a chromosome
Correct Answer: A DNA region where replication begins
Replication begins at specific DNA locations called origins of replication. Proteins assemble at
these sites and establish replication machinery. Eukaryotic chromosomes generally contain
multiple origins because their genomes are large and require efficient duplication.
8. Why can DNA replication proceed from multiple origins in a eukaryotic chromosome?
A. Multiple origins allow large chromosomes to be copied more efficiently.
B. Multiple origins prevent transcription.
C. Each origin produces a different genetic code.
D. Multiple origins eliminate the need for DNA polymerase.
Correct Answer: Multiple origins allow large chromosomes to be copied more efficiently.
, Large eukaryotic chromosomes would take too long to replicate from a single starting point.
Multiple origins allow replication forks to operate simultaneously at different chromosome
locations. This greatly reduces the time required to duplicate the genome.
9. In what direction does DNA polymerase synthesize a new DNA strand?
A. 3′ to 5′
B. 5′ to 5′
C. 3′ to 3′
D. 5′ to 3′
Correct Answer: 5′ to 3′
DNA polymerase adds nucleotides to the free 3′ hydroxyl group of the growing strand.
Consequently, the new strand is always synthesized in the 5′ to 3′ direction. This directional
requirement explains why leading and lagging strands are synthesized differently.
10. Why is an RNA primer necessary during DNA replication?
A. It provides a starting point with a free 3′ hydroxyl group for DNA polymerase.
B. It terminates replication.
C. It prevents DNA from unwinding.
D. It replaces the entire DNA template.
Correct Answer: It provides a starting point with a free 3′ hydroxyl group for DNA
polymerase.
DNA polymerase cannot initiate a completely new strand without an existing nucleotide
chain. Primase synthesizes a short RNA primer that provides the necessary 3′ hydroxyl group.
DNA polymerase then extends the primer using DNA nucleotides.
11. Which enzyme synthesizes the RNA primer used during DNA replication?
A. Helicase
B. Primase
C. Ligase
D. Topoisomerase
Correct Answer: Primase
Primase synthesizes short RNA primers complementary to the DNA template. These primers
provide the starting points required by DNA polymerase. After replication, the RNA primers
are removed and replaced with DNA.
