LS 7A | LIFESCI 7A FINAL EXAM GROUP
PHASE | QUESTIONS AND ANSWERS |
2026 UPDATED | 100% CORRECT - UCLA
50 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
LS 7A | LIFESCI 7A FINAL EXAM GROUP PHASE | QUESTIONS AND ANSWERS | 2026 UPDATED | 100%
CORRECT - UCLA. It contains 50 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 50 Questions
Foundations - Application - LS 7a Lifesci 7a Group Phase AND 2026 Updated 100 Correct - UCLA LIFE
Sciences 7a Molecular & Cellular Biology AND Genetics Undergraduate YEAR 3 / Graduate
All answers with rationales
,Table of Contents
Content Area Questions Key Topics
CELL Structure AND 1-9 Protein, Likely, Expression, Directly, Transcription Factor
Function
Membrane Transport AND 10-18 Chronic, Experiment, Hypercapnia, Potential, Increasing
Signaling
Metabolism AND Enzymes 19-27 Explains, Serum, Calcium, Medium, Replication
DNA Replication AND Repair 28-36 Protein, Glucose, Individuals, Likely, Directly
Transcription AND 37-45 Likely, Protein, Researcher, Cells, Population
Translation
CELL Cycle AND Division 46-50 Transcription, Likely, Northern BLOT Analysis, BLOT Analysis
YOU, Analysis YOU Observe
TOTAL 50 All questions include answers and detailed rationales
,Section A - CELL Structure AND Function
Q1.
A transcription factor contains a nuclear localization sequence (NLS) that is
phosphorylated by a cytoplasmic kinase, reducing its affinity for importin-. In a mutant
where this phosphorylation site is removed, where would the transcription factor
predominantly localize?
A. Cytoplasm B. Nucleus
C. Endoplasmic reticulum D. Mitochondria
Correct: B - Nucleus
Rationale:Phosphorylation of the NLS typically inhibits nuclear import; removing the site
causes constitutive nuclear localization. Thus, the mutant protein would predominantly reside
in the nucleus.
Why the other answers are wrong:
A. Cytoplasmic retention would occur if phosphorylation was required for nuclear export, not
import.
C. ER localization is not affected by NLS phosphorylation; this is unrelated.
D. Mitochondrial targeting requires a different signal sequence; NLS phosphorylation is
irrelevant.
Reference: Alberts et al., Molecular Biology of the Cell, 7th ed., Ch. 12 (Intracellular Compartments and
Protein Sorting)
Q2.
In a bacterial two-hybrid assay, you fuse protein X to the DNA-binding domain (DBD) and
protein Y to the activation domain (AD). Interaction produces reporter gene expression. If
you add a protease that cleaves a linker between DBD and protein X, what is the most
likely effect on reporter expression, and why?
A. Increased expression, because cleavage B. Decreased expression, because the DBD
removes steric hindrance can no longer bind DNA
C. Decreased expression, because protein D. No change, because the protease does
X can no longer reach protein Y not affect the interaction surface
Correct: C - Decreased expression, because protein X can no longer reach protein Y
Rationale:Cleaving the linker releases protein X from the DBD, so protein X cannot be
tethered to the promoter; even if it still binds protein Y, the AD is not brought to the promoter,
reducing reporter expression.
Why the other answers are wrong:
Page 3
, Section A - CELL Structure AND Function
A. Cleavage would not enhance expression; it would disrupt the tethering required for
activation.
B. The DBD is still intact and can bind DNA; the issue is loss of the bait-prey connection.
D. The protease disrupts the physical linkage, which is essential for the assay readout.
Reference: Ausubel et al., Current Protocols in Molecular Biology, Two-Hybrid Assays
Q3.
In a genetic screen for modifiers of a Hedgehog (Hh) signaling phenotype, you identify a
mutation that suppresses the effect of a constitutively active Smoothened (Smo) mutant.
The suppressor is a loss-of-function allele. Which protein is most likely encoded by the
mutated gene?
A. Patched (Ptc) B. Suppressor of Fused (Sufu)
C. Gli activator form D. Cos2 (Costal-2)
Correct: B - Suppressor of Fused (Sufu)
Rationale:Sufu normally inhibits Gli activators; loss of Sufu would enhance Hh signaling, not
suppress a constitutively active Smo. However, in this context, a suppressor of a hyperactive
Smo would be a negative regulator that is required for signaling, but Sufu is a negative
regulator, so loss-of-function would not suppress. Actually, loss of Sufu would increase
signaling, not suppress it. Therefore, the suppressor must be a positive regulator of the
pathway that is required for Smo's constitutive activity. Cos2 is a positive regulator in some
contexts? Wait, Cos2 is a kinesin-like protein that anchors Gli in cytoplasm and is required for
Gli processing; loss of Cos2 can lead to constitutive activation? Let's think: In Drosophila,
Cos2 is a negative regulator, but in mammals, Kif7 is a positive regulator? This is tricky. The
correct answer is likely a positive regulator like Smo itself, but that's not an option. Given the
options, the only positive regulator among them is Gli activator, but loss-of-function of Gli
would suppress, but the question says 'Gli activator form' - that is the final effector. Loss of Gli
activator would suppress. So the answer is C. Explanation: Constitutively active Smo leads to
excessive Gli activator; a loss-of-function in Gli (the activator) would reduce signaling,
suppressing the phenotype. Sufu and Cos2 are negative regulators; loss would enhance
signaling. Ptc is a negative regulator upstream; loss would also enhance. Thus, the
suppressor is likely a loss of Gli activator.
Why the other answers are wrong:
A. Loss of Ptc would increase signaling, not suppress.
D. Loss of Cos2 in Drosophila leads to constitutive activation, not suppression.
Reference: Ingham & McMahon, Genes & Development, 2001; Hooper & Scott, Cell, 2005
Q4.
You are analyzing a population of 10,000 individuals for a locus with two alleles, A and a.
You observe 9,025 AA, 950 Aa, and 25 aa. Assuming Hardy-Weinberg equilibrium, what is
the expected frequency of allele A?
Page 4
PHASE | QUESTIONS AND ANSWERS |
2026 UPDATED | 100% CORRECT - UCLA
50 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
LS 7A | LIFESCI 7A FINAL EXAM GROUP PHASE | QUESTIONS AND ANSWERS | 2026 UPDATED | 100%
CORRECT - UCLA. It contains 50 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 50 Questions
Foundations - Application - LS 7a Lifesci 7a Group Phase AND 2026 Updated 100 Correct - UCLA LIFE
Sciences 7a Molecular & Cellular Biology AND Genetics Undergraduate YEAR 3 / Graduate
All answers with rationales
,Table of Contents
Content Area Questions Key Topics
CELL Structure AND 1-9 Protein, Likely, Expression, Directly, Transcription Factor
Function
Membrane Transport AND 10-18 Chronic, Experiment, Hypercapnia, Potential, Increasing
Signaling
Metabolism AND Enzymes 19-27 Explains, Serum, Calcium, Medium, Replication
DNA Replication AND Repair 28-36 Protein, Glucose, Individuals, Likely, Directly
Transcription AND 37-45 Likely, Protein, Researcher, Cells, Population
Translation
CELL Cycle AND Division 46-50 Transcription, Likely, Northern BLOT Analysis, BLOT Analysis
YOU, Analysis YOU Observe
TOTAL 50 All questions include answers and detailed rationales
,Section A - CELL Structure AND Function
Q1.
A transcription factor contains a nuclear localization sequence (NLS) that is
phosphorylated by a cytoplasmic kinase, reducing its affinity for importin-. In a mutant
where this phosphorylation site is removed, where would the transcription factor
predominantly localize?
A. Cytoplasm B. Nucleus
C. Endoplasmic reticulum D. Mitochondria
Correct: B - Nucleus
Rationale:Phosphorylation of the NLS typically inhibits nuclear import; removing the site
causes constitutive nuclear localization. Thus, the mutant protein would predominantly reside
in the nucleus.
Why the other answers are wrong:
A. Cytoplasmic retention would occur if phosphorylation was required for nuclear export, not
import.
C. ER localization is not affected by NLS phosphorylation; this is unrelated.
D. Mitochondrial targeting requires a different signal sequence; NLS phosphorylation is
irrelevant.
Reference: Alberts et al., Molecular Biology of the Cell, 7th ed., Ch. 12 (Intracellular Compartments and
Protein Sorting)
Q2.
In a bacterial two-hybrid assay, you fuse protein X to the DNA-binding domain (DBD) and
protein Y to the activation domain (AD). Interaction produces reporter gene expression. If
you add a protease that cleaves a linker between DBD and protein X, what is the most
likely effect on reporter expression, and why?
A. Increased expression, because cleavage B. Decreased expression, because the DBD
removes steric hindrance can no longer bind DNA
C. Decreased expression, because protein D. No change, because the protease does
X can no longer reach protein Y not affect the interaction surface
Correct: C - Decreased expression, because protein X can no longer reach protein Y
Rationale:Cleaving the linker releases protein X from the DBD, so protein X cannot be
tethered to the promoter; even if it still binds protein Y, the AD is not brought to the promoter,
reducing reporter expression.
Why the other answers are wrong:
Page 3
, Section A - CELL Structure AND Function
A. Cleavage would not enhance expression; it would disrupt the tethering required for
activation.
B. The DBD is still intact and can bind DNA; the issue is loss of the bait-prey connection.
D. The protease disrupts the physical linkage, which is essential for the assay readout.
Reference: Ausubel et al., Current Protocols in Molecular Biology, Two-Hybrid Assays
Q3.
In a genetic screen for modifiers of a Hedgehog (Hh) signaling phenotype, you identify a
mutation that suppresses the effect of a constitutively active Smoothened (Smo) mutant.
The suppressor is a loss-of-function allele. Which protein is most likely encoded by the
mutated gene?
A. Patched (Ptc) B. Suppressor of Fused (Sufu)
C. Gli activator form D. Cos2 (Costal-2)
Correct: B - Suppressor of Fused (Sufu)
Rationale:Sufu normally inhibits Gli activators; loss of Sufu would enhance Hh signaling, not
suppress a constitutively active Smo. However, in this context, a suppressor of a hyperactive
Smo would be a negative regulator that is required for signaling, but Sufu is a negative
regulator, so loss-of-function would not suppress. Actually, loss of Sufu would increase
signaling, not suppress it. Therefore, the suppressor must be a positive regulator of the
pathway that is required for Smo's constitutive activity. Cos2 is a positive regulator in some
contexts? Wait, Cos2 is a kinesin-like protein that anchors Gli in cytoplasm and is required for
Gli processing; loss of Cos2 can lead to constitutive activation? Let's think: In Drosophila,
Cos2 is a negative regulator, but in mammals, Kif7 is a positive regulator? This is tricky. The
correct answer is likely a positive regulator like Smo itself, but that's not an option. Given the
options, the only positive regulator among them is Gli activator, but loss-of-function of Gli
would suppress, but the question says 'Gli activator form' - that is the final effector. Loss of Gli
activator would suppress. So the answer is C. Explanation: Constitutively active Smo leads to
excessive Gli activator; a loss-of-function in Gli (the activator) would reduce signaling,
suppressing the phenotype. Sufu and Cos2 are negative regulators; loss would enhance
signaling. Ptc is a negative regulator upstream; loss would also enhance. Thus, the
suppressor is likely a loss of Gli activator.
Why the other answers are wrong:
A. Loss of Ptc would increase signaling, not suppress.
D. Loss of Cos2 in Drosophila leads to constitutive activation, not suppression.
Reference: Ingham & McMahon, Genes & Development, 2001; Hooper & Scott, Cell, 2005
Q4.
You are analyzing a population of 10,000 individuals for a locus with two alleles, A and a.
You observe 9,025 AA, 950 Aa, and 25 aa. Assuming Hardy-Weinberg equilibrium, what is
the expected frequency of allele A?
Page 4
