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58 Questions with Answers and Detailed Rationales
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All answers with rationales
,Table of Contents
Content Area Questions Key Topics
Mendelian Genetics AND 1-10 Likely, Transcription, Factor, Kinase, Protein
Inheritance Patterns
Molecular Genetics DNA 11-20 Population, Frequency, Fitness, Allele, Researcher
Replication Transcription
AND Translation
GENE Expression AND 21-30 Recessive, Genetic, Likely, Mutation, Allele
Regulation
Population Genetics AND 31-40 Likely, Region, Protein, Mutant, Glucose
Hardy-weinberg Equilibrium
Evolutionary Mechanisms 41-50 Kinase, Mutation, Transcription, Likely, Protein
AND Speciation
Phylogenetics AND 51-58 Likely, Activation, Protein, Mutation, Treated
Systematics
TOTAL 58 All questions include answers and detailed rationales
,Section A - Mendelian Genetics AND Inheritance Patterns
Q1.
A chromatin immunoprecipitation (ChIP) experiment reveals that a transcription factor
binds to a distal enhancer in a tissue-specific manner. Yet, knockout of the factor does not
alter expression of the putative target gene. Which mechanism best explains this
observation?
A. The factor is a pioneer factor that only B. The binding is non-functional due to the
opens chromatin without recruiting absence of a required co-factor that bridges
co-activators. enhancer-promoter interaction.
C. The enhancer is active only during D. The factor binds as a monomer but
development and is silenced in adult tissue. requires homodimerization to activate
transcription.
Correct: B - The binding is non-functional due to the absence of a required co-factor that
bridges enhancer-promoter interaction.
Rationale:ChIP shows physical binding, but function requires recruitment of co-activators and
chromatin looping. If the co-factor is missing in the tested condition, binding is non-productive.
Pioneer factors still have functions; developmental silencing would show no binding in adult
tissue; monomer/dimer status doesn't explain the lack of effect.
Why the other answers are wrong:
A. Pioneer factors have chromatin-opening functions that would still affect expression, so this
does not explain the lack of effect.
C. If the enhancer were silenced, ChIP would not show binding in adult tissue.
D. Monomer/dimer status is not the primary reason for a complete lack of effect when binding
is present.
Reference: Alberts et al., Molecular Biology of the Cell, 7th Ed., Ch. 7
Q2.
A protein kinase is activated by phosphorylation at a conserved residue within its
activation loop. Mutation of this residue to alanine results in loss of kinase activity.
However, replacing the residue with glutamate partially restores activity. What is the most
likely role of this phosphorylation?
A. Induces a conformational change that B. Creates a binding site for a regulatory
opens the active site subunit
C. Targets the kinase for proteasomal D. Promotes nuclear localization of the
degradation kinase
Correct: A - Induces a conformational change that opens the active site
Page 3
, Section A - Mendelian Genetics AND Inheritance Patterns
Rationale: Glutamate mimics phosphoserine/threonine by providing a negative charge, which
often stabilizes the active conformation. Phosphorylation in the activation loop typically
rearranges the active site to allow substrate binding. The other options would not be
mimicked by a simple charge substitution.
Why the other answers are wrong:
B. Binding sites for regulatory subunits require specific residues beyond charge mimicry.
C. Phosphorylation that targets degradation would not be mimicked by glutamate.
D. Nuclear localization signals are not typically created by phosphorylation in the activation
loop.
Reference: Lehninger Principles of Biochemistry, 8th Ed., Ch. 12
Q3.
In a screen for genes that regulate cell size, you find a mutation that causes premature
entry into mitosis. Which of the following is the most likely direct target of the mutated
gene?
A. Cyclin-dependent kinase (CDK) activating B. Weel kinase
kinase (CAK)
C. p21 D. Retinoblastoma protein (Rb)
Correct: B - Weel kinase
Rationale:Weel phosphorylates and inhibits CDK, preventing mitotic entry. Loss of Weel
would cause premature mitosis. CAK activates CDK, so a loss would delay mitosis. p21 and
Rb inhibit cell cycle progression, so their loss would also promote entry, but they are not direct
regulators of mitotic CDK activity in the same way.
Why the other answers are wrong:
A. Loss of CAK would reduce CDK activation, delaying mitosis.
C. p21 loss affects G1/S transition, not directly mitosis.
D. Rb loss affects G1/S, not directly mitosis.
Reference: Morgan, The Cell Cycle: Principles of Control, Ch. 4
Q4.
A novel anti-cancer drug inhibits the proteasome. Which of the following downstream
effects is most likely to contribute to its therapeutic efficacy in cancers with high levels of
the transcription factor Myc?
A. Stabilization of cyclin D1, promoting cell B. Accumulation of p53 due to reduced
cycle progression degradation, leading to apoptosis
C. Inhibition of NF-B signaling by stabilizing D. Increased degradation of pro-apoptotic
IB factors
Correct: C - Inhibition of NF-B signaling by stabilizing IB
Page 4