BIOLOGY 251 LECTURE EXAM 2 | FULL
QUESTIONS AND ANSWERS WITH RATIONALES
| 2026/27 UPDATE | 100% CORRECT - WSU.
112 Questions with Answers and Detailed Rationales
100 PERCENT GUARANTEED PASS
INSTANT DOWNLOAD ANSWERS INCLUDED
IMPORTANCE OF THIS DOCUMENT
This comprehensive examination preparation guide has been meticulously developed to help you succeed in the
BIOLOGY 251 LECTURE EXAM 2 | FULL QUESTIONS AND ANSWERS WITH RATIONALES | 2026/27
UPDATE | 100% CORRECT - WSU.. It contains 112 carefully selected questions that reflect the most current
exam content and testing strategies. Each question is accompanied by a correct answer and a detailed rationale
that explains the underlying pathophysiology, pharmacology, or clinical reasoning.
Self-Assessment – Test your knowledge and Exam Preparation – Familiarize yourself with the
identify areas requiring further question format and content
study areas
Concept Reinforcement – Deepen your Confidence Building – Develop test-taking
understanding through strategies and reduce
evidence-based exam anxiety
rationales
Time Management – Practice answering
questions under simulated
exam conditions
Review Summary 112 Questions
Foundations - Application - Biology 251 Lecture 2 FULL AND WITH Rationales 2026/27 Update 100
Correct WSU Biology 251 Molecular AND Cellular Biology Undergraduate YEAR 3 / Graduate
All answers with rationales
,Table of Contents
Content Area Questions Key Topics
CELL Structure AND 1-19 Likely, Protein, Transcription, Factor, Binds
Function
Plasma Membrane AND 20-38 Mutation, Immediate, Researcher, Likely, Protein
Transport
Cellular Respiration AND 39-57 Mutation, Likely, Protein, Cells, Researcher
Metabolism
DNA Structure AND 58-76 Cells, Likely, Researcher, Protein, Sequence
Replication
GENE Expression AND 77-95 Kinase, Mutation, Protein, Directly, Likely
Protein Synthesis
CELL Cycle AND Mitosis 96-112 Likely, Mutation, Researcher, Embryos, Genetic
TOTAL 112 All questions include answers and detailed rationales
,Section A - CELL Structure AND Function
Q1.
A novel kinase inhibitor is found to block phosphorylation of a transcription factor that is
normally retained in the cytoplasm. Which post-translational modification is most likely
responsible for the nuclear localization of this transcription factor?
A. Acetylation of lysine residues B. Phosphorylation of serine residues
adjacent to a nuclear export signal
C. Sumoylation of lysine residues D. Ubiquitination of lysine residues
Correct: B - Phosphorylation of serine residues adjacent to a nuclear export signal
Rationale:Phosphorylation near a nuclear export signal can mask it, promoting nuclear
retention. Acetylation and sumoylation affect DNA binding and stability, but not typically NES
masking. Ubiquitination targets for degradation.
Q2.
In an in vitro actin polymerization assay, you add actin monomers with a fluorescent tag
and observe that polymerization is faster at the barbed end. Which protein addition would
most likely reverse this polarity by preferentially capping the barbed end?
A. Cofilin B. Gelsolin
C. Profilin D. Arp2/3 complex
Correct: B - Gelsolin
Rationale:Gelsolin caps the barbed end of actin filaments, preventing monomer addition
there, thus reversing the observed polarity. Cofilin severs filaments, profilin promotes
monomer addition to barbed ends, and Arp2/3 nucleates branches.
Q3.
A mutation in the promoter of a gene eliminates a binding site for a transcriptional
repressor. Which chromatin modification is most likely to be enriched at this promoter in
wild-type cells?
A. H3K4me3 B. H3K9me3
C. H3K27ac D. H2BK123ub1
Correct: B - H3K9me3
Page 3
, Section A - CELL Structure AND Function
Rationale: H3K9me3 is associated with heterochromatin and gene silencing, often enriched at
repressor-bound promoters. H3K4me3 and H3K27ac are marks of active transcription, and
H2BK123ub1 is involved in transcription elongation.
Q4.
You are studying a G protein-coupled receptor (GPCR) that activates phospholipase C.
Which second messenger cascade would be most directly initiated?
A. Increase in cAMP and activation of B. Increase in diacylglycerol and inositol
protein kinase A trisphosphate
C. Activation of receptor tyrosine kinase and D. Increase in nitric oxide and cGMP
Ras
Correct: B - Increase in diacylglycerol and inositol trisphosphate
Rationale:Phospholipase C cleaves PIP2 into DAG and IP3, which activate PKC and release
calcium. cAMP-PKA is from adenylyl cyclase, RTK-Ras is separate, and nitric oxide/cGMP is
another pathway.
Q5.
A cell line with a defective anaphase-promoting complex (APC/C) is arrested in mitosis.
Which of the following is the most likely consequence?
A. Inability to degrade cyclin B, maintaining B. Inability to phosphorylate cohesin,
CDK1 activity preventing sister chromatid separation
C. Inability to activate separase, leading to D. Inability to assemble the mitotic spindle
failure of chromosome segregation due to lack of tubulin polymerization
Correct: A - Inability to degrade cyclin B, maintaining CDK1 activity
Rationale:APC/C targets cyclin B for degradation, inactivating CDK1 to exit mitosis. While
APC/C also targets securin, the primary defect in APC/C loss is cyclin B persistence, which
keeps CDK1 active and blocks mitotic exit. Cohesin cleavage by separase is downstream of
securin degradation, but the APC/C defect directly prevents cyclin B degradation.
Q6.
In a screen for genes that affect cell migration, you identify a protein that localizes to the
leading edge and binds to both actin and microtubules. Which protein is this most likely
to be?
A. Kinesin-5 B. CLIP-170
C. Formin D. Dynein
Correct: B - CLIP-170
Page 4
QUESTIONS AND ANSWERS WITH RATIONALES
| 2026/27 UPDATE | 100% CORRECT - WSU.
112 Questions with Answers and Detailed Rationales
100 PERCENT GUARANTEED PASS
INSTANT DOWNLOAD ANSWERS INCLUDED
IMPORTANCE OF THIS DOCUMENT
This comprehensive examination preparation guide has been meticulously developed to help you succeed in the
BIOLOGY 251 LECTURE EXAM 2 | FULL QUESTIONS AND ANSWERS WITH RATIONALES | 2026/27
UPDATE | 100% CORRECT - WSU.. It contains 112 carefully selected questions that reflect the most current
exam content and testing strategies. Each question is accompanied by a correct answer and a detailed rationale
that explains the underlying pathophysiology, pharmacology, or clinical reasoning.
Self-Assessment – Test your knowledge and Exam Preparation – Familiarize yourself with the
identify areas requiring further question format and content
study areas
Concept Reinforcement – Deepen your Confidence Building – Develop test-taking
understanding through strategies and reduce
evidence-based exam anxiety
rationales
Time Management – Practice answering
questions under simulated
exam conditions
Review Summary 112 Questions
Foundations - Application - Biology 251 Lecture 2 FULL AND WITH Rationales 2026/27 Update 100
Correct WSU Biology 251 Molecular AND Cellular Biology Undergraduate YEAR 3 / Graduate
All answers with rationales
,Table of Contents
Content Area Questions Key Topics
CELL Structure AND 1-19 Likely, Protein, Transcription, Factor, Binds
Function
Plasma Membrane AND 20-38 Mutation, Immediate, Researcher, Likely, Protein
Transport
Cellular Respiration AND 39-57 Mutation, Likely, Protein, Cells, Researcher
Metabolism
DNA Structure AND 58-76 Cells, Likely, Researcher, Protein, Sequence
Replication
GENE Expression AND 77-95 Kinase, Mutation, Protein, Directly, Likely
Protein Synthesis
CELL Cycle AND Mitosis 96-112 Likely, Mutation, Researcher, Embryos, Genetic
TOTAL 112 All questions include answers and detailed rationales
,Section A - CELL Structure AND Function
Q1.
A novel kinase inhibitor is found to block phosphorylation of a transcription factor that is
normally retained in the cytoplasm. Which post-translational modification is most likely
responsible for the nuclear localization of this transcription factor?
A. Acetylation of lysine residues B. Phosphorylation of serine residues
adjacent to a nuclear export signal
C. Sumoylation of lysine residues D. Ubiquitination of lysine residues
Correct: B - Phosphorylation of serine residues adjacent to a nuclear export signal
Rationale:Phosphorylation near a nuclear export signal can mask it, promoting nuclear
retention. Acetylation and sumoylation affect DNA binding and stability, but not typically NES
masking. Ubiquitination targets for degradation.
Q2.
In an in vitro actin polymerization assay, you add actin monomers with a fluorescent tag
and observe that polymerization is faster at the barbed end. Which protein addition would
most likely reverse this polarity by preferentially capping the barbed end?
A. Cofilin B. Gelsolin
C. Profilin D. Arp2/3 complex
Correct: B - Gelsolin
Rationale:Gelsolin caps the barbed end of actin filaments, preventing monomer addition
there, thus reversing the observed polarity. Cofilin severs filaments, profilin promotes
monomer addition to barbed ends, and Arp2/3 nucleates branches.
Q3.
A mutation in the promoter of a gene eliminates a binding site for a transcriptional
repressor. Which chromatin modification is most likely to be enriched at this promoter in
wild-type cells?
A. H3K4me3 B. H3K9me3
C. H3K27ac D. H2BK123ub1
Correct: B - H3K9me3
Page 3
, Section A - CELL Structure AND Function
Rationale: H3K9me3 is associated with heterochromatin and gene silencing, often enriched at
repressor-bound promoters. H3K4me3 and H3K27ac are marks of active transcription, and
H2BK123ub1 is involved in transcription elongation.
Q4.
You are studying a G protein-coupled receptor (GPCR) that activates phospholipase C.
Which second messenger cascade would be most directly initiated?
A. Increase in cAMP and activation of B. Increase in diacylglycerol and inositol
protein kinase A trisphosphate
C. Activation of receptor tyrosine kinase and D. Increase in nitric oxide and cGMP
Ras
Correct: B - Increase in diacylglycerol and inositol trisphosphate
Rationale:Phospholipase C cleaves PIP2 into DAG and IP3, which activate PKC and release
calcium. cAMP-PKA is from adenylyl cyclase, RTK-Ras is separate, and nitric oxide/cGMP is
another pathway.
Q5.
A cell line with a defective anaphase-promoting complex (APC/C) is arrested in mitosis.
Which of the following is the most likely consequence?
A. Inability to degrade cyclin B, maintaining B. Inability to phosphorylate cohesin,
CDK1 activity preventing sister chromatid separation
C. Inability to activate separase, leading to D. Inability to assemble the mitotic spindle
failure of chromosome segregation due to lack of tubulin polymerization
Correct: A - Inability to degrade cyclin B, maintaining CDK1 activity
Rationale:APC/C targets cyclin B for degradation, inactivating CDK1 to exit mitosis. While
APC/C also targets securin, the primary defect in APC/C loss is cyclin B persistence, which
keeps CDK1 active and blocks mitotic exit. Cohesin cleavage by separase is downstream of
securin degradation, but the APC/C defect directly prevents cyclin B degradation.
Q6.
In a screen for genes that affect cell migration, you identify a protein that localizes to the
leading edge and binds to both actin and microtubules. Which protein is this most likely
to be?
A. Kinesin-5 B. CLIP-170
C. Formin D. Dynein
Correct: B - CLIP-170
Page 4
