BIOLOGY 251 LECTURE EXAM 4 (FINAL) | FULL
QUESTIONS, CORRECT ANSWERS, AND
RATIONALES | 2026 UPDATE | 100% CORRECT - WSU.
140 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 4 (FINAL) | FULL QUESTIONS, CORRECT ANSWERS, AND RATIONALES |
2026 UPDATE | 100% CORRECT - WSU.. It contains 140 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 140 Questions
Foundations - Application - Biology 251 Lecture 4 FULL Correct AND Rationales 2026 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
Animal FORM AND Function 1-24 Mutation, Population, Likely, Cells, Species
Homeostasis AND Endocrine 25-48 Species, Likely, Protein, Bacterial, Expected
System
Nervous System AND 49-72 Likely, Effect, Protein, Researcher, Directly
Sensory Physiology
Musculoskeletal System 73-96 Directly, Plasma, Inulin, Clearance, Primary
Circulatory AND Respiratory 97-120 Mutation, Population, Researcher, Expected, Studying
Systems
Digestive AND Excretory 121-140 Likely, Researcher, Mutation, Bacterial, Inhibits
Systems
TOTAL 140 All questions include answers and detailed rationales
,Section A - Animal FORM AND Function
Q1.
In a study of a novel receptor tyrosine kinase (RTK), you find that a point mutation in the
kinase domain abolishes autophosphorylation but still allows ligand-induced
dimerization. However, downstream activation of Ras is severely impaired. Which of the
following best explains this observation?
A. Dimerization alone is insufficient for B. The mutation prevents receptor
trans-autophosphorylation, which is required internalization, thereby reducing signaling.
for Grb2-SOS recruitment.
C. Ras activation requires direct binding of D. Ligand-induced dimerization normally
the RTK to Ras, which is disrupted. activates Ras via a kinase-independent
mechanism.
Correct: A - Dimerization alone is insufficient for trans-autophosphorylation, which is
required for Grb2-SOS recruitment.
Rationale:Autophosphorylation of RTKs creates docking sites for adaptor proteins like Grb2,
which recruit SOS to activate Ras. Dimerization without kinase activity fails to create these
sites, so Ras activation is impaired. The other options are not supported by standard RTK
signaling mechanisms.
Q2.
A researcher treats cells with a drug that inhibits DNA methyltransferase (DNMT) and
observes reactivation of a previously silenced tumor suppressor gene. Which of the
following chromatin modifications is most likely associated with the reactivation?
A. Increased H3K9me3 and HP1 binding at B. Increased H3K4me3 and histone
the promoter acetylation at the promoter
C. Decreased H3K27me3 and increased D. Increased H3K9me2 and decreased
DNA methylation H3K4me3 at the promoter
Correct: B - Increased H3K4me3 and histone acetylation at the promoter
Rationale:DNA methylation typically correlates with repressive chromatin (e.g., H3K9me3)
and gene silencing. Inhibiting DNMT leads to loss of methylation and a shift to active marks
like H3K4me3 and histone acetylation, allowing gene expression. The other options describe
repressive or mixed states.
Q3.
In a genetic screen, you identify a mutation in a gene encoding a component of the
spliceosome. Cells with this mutation show accumulation of unspliced pre-mRNA. Which
of the following processes is directly affected?
Page 3
, Section A - Animal FORM AND Function
A. Alternative polyadenylation B. RNA editing
C. Intron removal D. 5' capping
Correct: C - Intron removal
Rationale:The spliceosome is responsible for removing introns from pre-mRNA. A mutation in
a spliceosome component would impair intron removal, leading to accumulation of unspliced
pre-mRNA. The other processes are distinct and not directly affected by spliceosome
mutations.
Q4.
A patient with a family history of early-onset breast cancer is found to have a germline
mutation in BRCA1. This mutation impairs the protein's E3 ubiquitin ligase activity. Which
of the following DNA repair pathways is most directly compromised?
A. Base excision repair (BER) B. Nucleotide excision repair (NER)
C. Homologous recombination (HR) D. Non-homologous end joining (NHEJ)
Correct: C - Homologous recombination (HR)
Rationale:BRCA1 plays a critical role in homologous recombination repair of double-strand
breaks. Its E3 ligase activity is involved in recruiting repair factors. Impairment of this activity
compromises HR, leading to genomic instability and cancer predisposition. BER and NER are
not primarily affected by BRCA1 mutations.
Q5.
Which of the following experimental results would provide the strongest evidence that a
small non-coding RNA regulates gene expression via translational repression rather than
mRNA degradation?
A. The target mRNA levels are unchanged, B. The target mRNA levels decrease, and
but protein levels decrease. protein levels decrease proportionally.
C. The target mRNA is cleaved at a specific D. The target mRNA is polyadenylated but
site within the coding sequence. not exported from the nucleus.
Correct: A - The target mRNA levels are unchanged, but protein levels decrease.
Rationale:Translational repression reduces protein synthesis without affecting mRNA stability,
so mRNA levels remain constant while protein levels drop. The other options indicate mRNA
degradation or cleavage, which are characteristic of siRNA-mediated silencing or other
mechanisms.
Page 4
QUESTIONS, CORRECT ANSWERS, AND
RATIONALES | 2026 UPDATE | 100% CORRECT - WSU.
140 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 4 (FINAL) | FULL QUESTIONS, CORRECT ANSWERS, AND RATIONALES |
2026 UPDATE | 100% CORRECT - WSU.. It contains 140 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 140 Questions
Foundations - Application - Biology 251 Lecture 4 FULL Correct AND Rationales 2026 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
Animal FORM AND Function 1-24 Mutation, Population, Likely, Cells, Species
Homeostasis AND Endocrine 25-48 Species, Likely, Protein, Bacterial, Expected
System
Nervous System AND 49-72 Likely, Effect, Protein, Researcher, Directly
Sensory Physiology
Musculoskeletal System 73-96 Directly, Plasma, Inulin, Clearance, Primary
Circulatory AND Respiratory 97-120 Mutation, Population, Researcher, Expected, Studying
Systems
Digestive AND Excretory 121-140 Likely, Researcher, Mutation, Bacterial, Inhibits
Systems
TOTAL 140 All questions include answers and detailed rationales
,Section A - Animal FORM AND Function
Q1.
In a study of a novel receptor tyrosine kinase (RTK), you find that a point mutation in the
kinase domain abolishes autophosphorylation but still allows ligand-induced
dimerization. However, downstream activation of Ras is severely impaired. Which of the
following best explains this observation?
A. Dimerization alone is insufficient for B. The mutation prevents receptor
trans-autophosphorylation, which is required internalization, thereby reducing signaling.
for Grb2-SOS recruitment.
C. Ras activation requires direct binding of D. Ligand-induced dimerization normally
the RTK to Ras, which is disrupted. activates Ras via a kinase-independent
mechanism.
Correct: A - Dimerization alone is insufficient for trans-autophosphorylation, which is
required for Grb2-SOS recruitment.
Rationale:Autophosphorylation of RTKs creates docking sites for adaptor proteins like Grb2,
which recruit SOS to activate Ras. Dimerization without kinase activity fails to create these
sites, so Ras activation is impaired. The other options are not supported by standard RTK
signaling mechanisms.
Q2.
A researcher treats cells with a drug that inhibits DNA methyltransferase (DNMT) and
observes reactivation of a previously silenced tumor suppressor gene. Which of the
following chromatin modifications is most likely associated with the reactivation?
A. Increased H3K9me3 and HP1 binding at B. Increased H3K4me3 and histone
the promoter acetylation at the promoter
C. Decreased H3K27me3 and increased D. Increased H3K9me2 and decreased
DNA methylation H3K4me3 at the promoter
Correct: B - Increased H3K4me3 and histone acetylation at the promoter
Rationale:DNA methylation typically correlates with repressive chromatin (e.g., H3K9me3)
and gene silencing. Inhibiting DNMT leads to loss of methylation and a shift to active marks
like H3K4me3 and histone acetylation, allowing gene expression. The other options describe
repressive or mixed states.
Q3.
In a genetic screen, you identify a mutation in a gene encoding a component of the
spliceosome. Cells with this mutation show accumulation of unspliced pre-mRNA. Which
of the following processes is directly affected?
Page 3
, Section A - Animal FORM AND Function
A. Alternative polyadenylation B. RNA editing
C. Intron removal D. 5' capping
Correct: C - Intron removal
Rationale:The spliceosome is responsible for removing introns from pre-mRNA. A mutation in
a spliceosome component would impair intron removal, leading to accumulation of unspliced
pre-mRNA. The other processes are distinct and not directly affected by spliceosome
mutations.
Q4.
A patient with a family history of early-onset breast cancer is found to have a germline
mutation in BRCA1. This mutation impairs the protein's E3 ubiquitin ligase activity. Which
of the following DNA repair pathways is most directly compromised?
A. Base excision repair (BER) B. Nucleotide excision repair (NER)
C. Homologous recombination (HR) D. Non-homologous end joining (NHEJ)
Correct: C - Homologous recombination (HR)
Rationale:BRCA1 plays a critical role in homologous recombination repair of double-strand
breaks. Its E3 ligase activity is involved in recruiting repair factors. Impairment of this activity
compromises HR, leading to genomic instability and cancer predisposition. BER and NER are
not primarily affected by BRCA1 mutations.
Q5.
Which of the following experimental results would provide the strongest evidence that a
small non-coding RNA regulates gene expression via translational repression rather than
mRNA degradation?
A. The target mRNA levels are unchanged, B. The target mRNA levels decrease, and
but protein levels decrease. protein levels decrease proportionally.
C. The target mRNA is cleaved at a specific D. The target mRNA is polyadenylated but
site within the coding sequence. not exported from the nucleus.
Correct: A - The target mRNA levels are unchanged, but protein levels decrease.
Rationale:Translational repression reduces protein synthesis without affecting mRNA stability,
so mRNA levels remain constant while protein levels drop. The other options indicate mRNA
degradation or cleavage, which are characteristic of siRNA-mediated silencing or other
mechanisms.
Page 4
