Test Bank For Cell Biology, 4th Edition
Authors: Thomas D. Pollard,William C. Earnshaw,Jennifer Lippincott-
Schwartz,Graham Johnson
,Chapter 1: Cells as the Basis of Life on Earth (Cell Biology, 4th Ed.)
MCQs (1–30)
1. DNA replication fidelity is primarily ensured by:
A. Helicase activity
B. DNA polymerase proofreading
C. RNA primase specificity
D. Ligase activity
Answer: B
Explanation (Step-by-step):
• DNA polymerase possesses 3′→5′ exonuclease activity
• Removes mismatched nucleotides → increases fidelity
• Works during elongation
Why others are wrong:
• A: Helicase unwinds DNA, no proofreading
• C: Primase synthesizes RNA primers only
• D: Ligase joins fragments
Disease link: Defects → mutator phenotype → cancer
Experimental relevance: Polymerase mutants used in fidelity assays
2. Chromatin accessibility is increased by:
A. DNA methylation
B. Histone deacetylation
C. Histone acetylation
D. Nucleosome compaction
Answer: C
Explanation:
, • Acetylation neutralizes histone positive charge
• Weakens DNA–histone interaction → open chromatin
Incorrect:
• A: represses transcription
• B: condenses chromatin
• D: reduces accessibility
Disease: Cancer epigenetics
Experiment: ChIP-seq shows acetylation marks
3. Phase separation in cells leads to:
A. Membrane-bound organelles
B. Protein aggregation into insoluble complexes
C. Formation of biomolecular condensates
D. DNA replication initiation
Answer: C
Explanation:
• Weak multivalent interactions → liquid-like droplets
• No membrane required
Incorrect:
• A: membrane-bound compartments
• B: pathological aggregation
• D: unrelated
Disease: Neurodegeneration (ALS)
Experiment: Fluorescence microscopy shows droplet dynamics
4. Intrinsically disordered proteins (IDPs) are characterized by:
, A. Stable tertiary structure
B. High rigidity
C. Structural flexibility
D. Lack of function
Answer: C
Explanation:
• IDPs lack fixed structure → enable signaling flexibility
• Participate in phase separation
Incorrect:
• A/B: opposite
• D: false
Disease: Alzheimer’s (tau protein)
5. The rate-limiting step of transcription is:
A. Elongation
B. Termination
C. Initiation
D. RNA splicing
Answer: C
Explanation:
• Requires transcription factor assembly
• RNA Pol II recruitment
Incorrect:
• A/B/D: downstream
Disease: Cancer transcription dysregulation
6. RNA splicing occurs in:
Authors: Thomas D. Pollard,William C. Earnshaw,Jennifer Lippincott-
Schwartz,Graham Johnson
,Chapter 1: Cells as the Basis of Life on Earth (Cell Biology, 4th Ed.)
MCQs (1–30)
1. DNA replication fidelity is primarily ensured by:
A. Helicase activity
B. DNA polymerase proofreading
C. RNA primase specificity
D. Ligase activity
Answer: B
Explanation (Step-by-step):
• DNA polymerase possesses 3′→5′ exonuclease activity
• Removes mismatched nucleotides → increases fidelity
• Works during elongation
Why others are wrong:
• A: Helicase unwinds DNA, no proofreading
• C: Primase synthesizes RNA primers only
• D: Ligase joins fragments
Disease link: Defects → mutator phenotype → cancer
Experimental relevance: Polymerase mutants used in fidelity assays
2. Chromatin accessibility is increased by:
A. DNA methylation
B. Histone deacetylation
C. Histone acetylation
D. Nucleosome compaction
Answer: C
Explanation:
, • Acetylation neutralizes histone positive charge
• Weakens DNA–histone interaction → open chromatin
Incorrect:
• A: represses transcription
• B: condenses chromatin
• D: reduces accessibility
Disease: Cancer epigenetics
Experiment: ChIP-seq shows acetylation marks
3. Phase separation in cells leads to:
A. Membrane-bound organelles
B. Protein aggregation into insoluble complexes
C. Formation of biomolecular condensates
D. DNA replication initiation
Answer: C
Explanation:
• Weak multivalent interactions → liquid-like droplets
• No membrane required
Incorrect:
• A: membrane-bound compartments
• B: pathological aggregation
• D: unrelated
Disease: Neurodegeneration (ALS)
Experiment: Fluorescence microscopy shows droplet dynamics
4. Intrinsically disordered proteins (IDPs) are characterized by:
, A. Stable tertiary structure
B. High rigidity
C. Structural flexibility
D. Lack of function
Answer: C
Explanation:
• IDPs lack fixed structure → enable signaling flexibility
• Participate in phase separation
Incorrect:
• A/B: opposite
• D: false
Disease: Alzheimer’s (tau protein)
5. The rate-limiting step of transcription is:
A. Elongation
B. Termination
C. Initiation
D. RNA splicing
Answer: C
Explanation:
• Requires transcription factor assembly
• RNA Pol II recruitment
Incorrect:
• A/B/D: downstream
Disease: Cancer transcription dysregulation
6. RNA splicing occurs in:
