BIOL 304: MOLECULAR CELL BIOLOGY
COMPREHENSIVE FINAL EXAMINATION
(2026 UPDATE)
Section I: Multiple Choice (55 Questions)
1. Which of the following experimental outcomes provided the strongest evidence that DNA, not
protein, is the genetic material?
a) The transforming principle in Streptococcus pneumoniae was destroyed by protease.
b) The transforming principle in Streptococcus pneumoniae was destroyed by DNase.
c) Bacteriophage proteins were injected into bacteria during infection.
d) Radioactive sulfur was found inside infected bacteria after phage infection.
Answer: b) The transforming principle in Streptococcus pneumoniae was destroyed by DNase.
Rationale: The Avery-MacLeod-McCarty experiment showed that only DNase (which destroys DNA)
eliminated the transforming ability, proving DNA is the transformative agent. Option d describes the
Hershey-Chase experiment, which confirmed DNA enters the cell, but option b directly identifies the
molecular nature of the heritable substance.
2. During DNA replication in eukaryotes, the enzyme responsible for synthesizing RNA primers is:
a) DNA polymerase α
b) DNA polymerase δ
c) Primase
d) Topoisomerase II
Answer: c) Primase
Rationale: Primase is the RNA polymerase that synthesizes short RNA primers. While DNA polymerase α
has primase activity associated with it in a complex, the core enzymatic activity that creates the RNA
oligonucleotide is primase.
3. Which histone protein is NOT part of the nucleosome core particle?
a) H2A
b) H2B
c) H3
d) H1
,Answer: d) H1
Rationale: The nucleosome core consists of an octamer of two copies each of H2A, H2B, H3, and H4.
Histone H1 (the linker histone) binds to the linker DNA between nucleosomes to facilitate higher-order
chromatin compaction.
4. A mutation occurs in the spliceosome complex that prevents the recognition of the 3’ splice site.
What is the most likely consequence?
a) Introns will be retained in the mature mRNA.
b) Exons will be skipped randomly.
c) Transcription will terminate prematurely.
d) Polyadenylation will fail.
Answer: a) Introns will be retained in the mature mRNA.
Rationale: If the spliceosome fails to recognize the 3’ splice site, the intron cannot be excised. This
results in intron retention, leading to a non-functional or truncated protein upon translation.
5. Which second messenger is directly produced by the enzyme adenylyl cyclase?
a) Inositol trisphosphate (IP3)
b) Diacylglycerol (DAG)
c) Cyclic AMP (cAMP)
d) Calcium ions (Ca2+)
Answer: c) Cyclic AMP (cAMP)
Rationale: Adenylyl cyclase converts ATP to cyclic AMP (cAMP). IP3 and DAG are produced by
phospholipase C, and calcium is released from intracellular stores.
6. Receptor Tyrosine Kinases (RTKs) typically initiate signaling by:
a) Opening ion channels upon ligand binding.
b) Activating G-proteins directly.
c) Dimerizing and autophosphorylating tyrosine residues.
d) Translocating to the nucleus to bind DNA.
Answer: c) Dimerizing and autophosphorylating tyrosine residues.
Rationale: Ligand binding induces dimerization of RTKs, which activates the intrinsic kinase domain,
leading to cross-autophosphorylation of specific tyrosine residues that serve as docking sites for
downstream signaling proteins (e.g., Grb2, PI3K).
7. The smooth endoplasmic reticulum (SER) is primarily responsible for:
a) Protein synthesis and folding.
b) Lipid synthesis and calcium storage.
c) Protein degradation.
d) ATP synthesis.
Answer: b) Lipid synthesis and calcium storage.
, Rationale: The SER is involved in lipid biosynthesis, detoxification processes, and sequestering calcium
ions (important in muscle contraction). Protein synthesis/folding occurs in the rough ER (RER).
8. Which cytoskeletal component is composed of tubulin dimers and exhibits dynamic instability?
a) Microfilaments (Actin)
b) Intermediate filaments
c) Microtubules
d) Septins
Answer: c) Microtubules
Rationale: Microtubules are polymers of α/β-tubulin that exhibit dynamic instability—rapid switching
between growth (polymerization) and shrinkage (depolymerization). Actin filaments exhibit treadmilling,
which is different from dynamic instability.
9. The "fluid mosaic model" describes the:
a) Replication of DNA in a semi-conservative manner.
b) Structure of the plasma membrane as a lipid bilayer with mobile proteins.
c) Flow of genetic information from DNA to RNA to protein.
d) Mechanism of cell migration.
Answer: b) Structure of the plasma membrane as a lipid bilayer with mobile proteins.
Rationale: Proposed by Singer and Nicolson, the fluid mosaic model states that the membrane is a fluid
lipid bilayer with proteins embedded within it that can move laterally ("float") within the layer.
10. During apoptosis, cytochrome c is released from the mitochondria to:
a) Activate caspases via the intrinsic pathway.
b) Provide energy for the dying cell.
c) Trigger inflammation.
d) Degrade nuclear DNA directly.
Answer: a) Activate caspases via the intrinsic pathway.
Rationale: Cytochrome c is released from the mitochondrial intermembrane space into the cytosol,
where it binds to Apaf-1 to form the apoptosome, which activates initiator caspase-9, leading to effector
caspase activation.
11. Which of the following is a characteristic of cancer cells?
a) Density-dependent inhibition of growth.
b) Anchorage dependence.
c) Loss of contact inhibition.
d) Quiescence in G0 phase.
Answer: c) Loss of contact inhibition.
Rationale: Cancer cells continue to proliferate even when in contact with other cells (loss of contact
inhibition), whereas normal cells stop dividing once they form a monolayer (density-dependent
inhibition).
COMPREHENSIVE FINAL EXAMINATION
(2026 UPDATE)
Section I: Multiple Choice (55 Questions)
1. Which of the following experimental outcomes provided the strongest evidence that DNA, not
protein, is the genetic material?
a) The transforming principle in Streptococcus pneumoniae was destroyed by protease.
b) The transforming principle in Streptococcus pneumoniae was destroyed by DNase.
c) Bacteriophage proteins were injected into bacteria during infection.
d) Radioactive sulfur was found inside infected bacteria after phage infection.
Answer: b) The transforming principle in Streptococcus pneumoniae was destroyed by DNase.
Rationale: The Avery-MacLeod-McCarty experiment showed that only DNase (which destroys DNA)
eliminated the transforming ability, proving DNA is the transformative agent. Option d describes the
Hershey-Chase experiment, which confirmed DNA enters the cell, but option b directly identifies the
molecular nature of the heritable substance.
2. During DNA replication in eukaryotes, the enzyme responsible for synthesizing RNA primers is:
a) DNA polymerase α
b) DNA polymerase δ
c) Primase
d) Topoisomerase II
Answer: c) Primase
Rationale: Primase is the RNA polymerase that synthesizes short RNA primers. While DNA polymerase α
has primase activity associated with it in a complex, the core enzymatic activity that creates the RNA
oligonucleotide is primase.
3. Which histone protein is NOT part of the nucleosome core particle?
a) H2A
b) H2B
c) H3
d) H1
,Answer: d) H1
Rationale: The nucleosome core consists of an octamer of two copies each of H2A, H2B, H3, and H4.
Histone H1 (the linker histone) binds to the linker DNA between nucleosomes to facilitate higher-order
chromatin compaction.
4. A mutation occurs in the spliceosome complex that prevents the recognition of the 3’ splice site.
What is the most likely consequence?
a) Introns will be retained in the mature mRNA.
b) Exons will be skipped randomly.
c) Transcription will terminate prematurely.
d) Polyadenylation will fail.
Answer: a) Introns will be retained in the mature mRNA.
Rationale: If the spliceosome fails to recognize the 3’ splice site, the intron cannot be excised. This
results in intron retention, leading to a non-functional or truncated protein upon translation.
5. Which second messenger is directly produced by the enzyme adenylyl cyclase?
a) Inositol trisphosphate (IP3)
b) Diacylglycerol (DAG)
c) Cyclic AMP (cAMP)
d) Calcium ions (Ca2+)
Answer: c) Cyclic AMP (cAMP)
Rationale: Adenylyl cyclase converts ATP to cyclic AMP (cAMP). IP3 and DAG are produced by
phospholipase C, and calcium is released from intracellular stores.
6. Receptor Tyrosine Kinases (RTKs) typically initiate signaling by:
a) Opening ion channels upon ligand binding.
b) Activating G-proteins directly.
c) Dimerizing and autophosphorylating tyrosine residues.
d) Translocating to the nucleus to bind DNA.
Answer: c) Dimerizing and autophosphorylating tyrosine residues.
Rationale: Ligand binding induces dimerization of RTKs, which activates the intrinsic kinase domain,
leading to cross-autophosphorylation of specific tyrosine residues that serve as docking sites for
downstream signaling proteins (e.g., Grb2, PI3K).
7. The smooth endoplasmic reticulum (SER) is primarily responsible for:
a) Protein synthesis and folding.
b) Lipid synthesis and calcium storage.
c) Protein degradation.
d) ATP synthesis.
Answer: b) Lipid synthesis and calcium storage.
, Rationale: The SER is involved in lipid biosynthesis, detoxification processes, and sequestering calcium
ions (important in muscle contraction). Protein synthesis/folding occurs in the rough ER (RER).
8. Which cytoskeletal component is composed of tubulin dimers and exhibits dynamic instability?
a) Microfilaments (Actin)
b) Intermediate filaments
c) Microtubules
d) Septins
Answer: c) Microtubules
Rationale: Microtubules are polymers of α/β-tubulin that exhibit dynamic instability—rapid switching
between growth (polymerization) and shrinkage (depolymerization). Actin filaments exhibit treadmilling,
which is different from dynamic instability.
9. The "fluid mosaic model" describes the:
a) Replication of DNA in a semi-conservative manner.
b) Structure of the plasma membrane as a lipid bilayer with mobile proteins.
c) Flow of genetic information from DNA to RNA to protein.
d) Mechanism of cell migration.
Answer: b) Structure of the plasma membrane as a lipid bilayer with mobile proteins.
Rationale: Proposed by Singer and Nicolson, the fluid mosaic model states that the membrane is a fluid
lipid bilayer with proteins embedded within it that can move laterally ("float") within the layer.
10. During apoptosis, cytochrome c is released from the mitochondria to:
a) Activate caspases via the intrinsic pathway.
b) Provide energy for the dying cell.
c) Trigger inflammation.
d) Degrade nuclear DNA directly.
Answer: a) Activate caspases via the intrinsic pathway.
Rationale: Cytochrome c is released from the mitochondrial intermembrane space into the cytosol,
where it binds to Apaf-1 to form the apoptosome, which activates initiator caspase-9, leading to effector
caspase activation.
11. Which of the following is a characteristic of cancer cells?
a) Density-dependent inhibition of growth.
b) Anchorage dependence.
c) Loss of contact inhibition.
d) Quiescence in G0 phase.
Answer: c) Loss of contact inhibition.
Rationale: Cancer cells continue to proliferate even when in contact with other cells (loss of contact
inhibition), whereas normal cells stop dividing once they form a monolayer (density-dependent
inhibition).
