1
NR507 / NR 507 Midterm ACTUAL EXAM
2026/2027 | Advanced Pathophysiology | Verified
Questions and Answers 100% Correct | Grade A |
Chamberlain | Pass Guaranteed
Section 1: Cellular & Genetic Mechanisms of Disease (Questions 1-20)
Question 1
A 35-year-old patient presents with neurodegenerative symptoms and progressive myoclonic
epilepsy. Genetic testing reveals an expansion of a trinucleotide repeat (CAG) on chromosome 4.
Which molecular mechanism best explains the pathogenesis of this disorder?
A. Methylation-induced gene silencing
B. Gain-of-function toxicity from expanded polyglutamine tract
C. Loss of tumor suppressor function
D. Genomic imprinting with maternal uniparental disomy
Correct Answer: B
Rationale: The CAG trinucleotide repeat expansion on chromosome 4 characterizes Huntington
disease, where the expanded polyglutamine tract in the huntingtin protein confers a toxic gain-of-
function. The mutant protein misfolds, aggregates in neuronal nuclei and cytoplasm, disrupts
proteasome function, impairs mitochondrial dynamics, and interferes with transcriptional
regulation, leading to striatal neuronal death through multiple downstream mechanisms including
excitotoxicity and altered gene expression.
Question 2
In acute cellular injury, which intracellular event represents the "point of no return" marking
irreversible injury before morphological evidence of necrosis becomes visible?
A. Depletion of ATP stores
B. Influx of calcium ions and activation of phospholipases
C. Loss of mitochondrial membrane potential and inability to reverse mitochondrial permeability
transition pore (mPTP) opening
D. Accumulation of reactive oxygen species
,2
Correct Answer: C
Rationale: The opening of the mitochondrial permeability transition pore (mPTP) represents the
critical irreversible step in cell injury. Once the mPTP opens persistently, mitochondrial
membrane potential collapses, oxidative phosphorylation ceases permanently, cytochrome c and
other pro-apoptotic factors leak into the cytosol, and cellular energy metabolism cannot be
restored regardless of reperfusion or removal of the injurious stimulus, committing the cell to
death.
Question 3
A researcher observes that exposure to hypoxia induces programmed cell death in myocardial
cells characterized by cell shrinkage, chromatin condensation, membrane blebbing, and
formation of apoptotic bodies without inflammation. Which caspase activation pathway is
primarily responsible for initiating this process in response to hypoxic injury?
A. Extrinsic pathway via Fas/Fas ligand interaction
B. Intrinsic (mitochondrial) pathway via Bcl-2 family protein modulation and cytochrome c
release
C. Inflammatory caspase pathway via NLRP3 inflammasome
D. Granzyme B-mediated pathway
Correct Answer: B
Rationale: Hypoxia-induced apoptosis in cardiomyocytes primarily occurs through the intrinsic
mitochondrial pathway. Hypoxia triggers Bcl-2 family protein dysregulation with increased
Bax/Bak oligomerization and decreased Bcl-2/Bcl-xL anti-apoptotic function, causing
mitochondrial outer membrane permeabilization, cytochrome c release into cytosol, apoptosome
formation with Apaf-1, and sequential activation of initiator caspase-9 followed by executioner
caspases-3 and -7, culminating in the characteristic apoptotic morphology.
Question 4
Which epigenetic modification involves the addition of methyl groups to cytosine residues in
CpG islands, typically resulting in long-term transcriptional silencing of tumor suppressor genes
in cancer pathogenesis?
A. Histone acetylation
B. DNA methylation
C. Histone methylation at H3K4me3
D. Chromatin remodeling via SWI/SNF complex
,3
Correct Answer: B
Rationale: DNA methylation at CpG islands in gene promoter regions represents the primary
epigenetic mechanism for stable gene silencing. DNA methyltransferases (DNMTs) catalyze the
addition of methyl groups to cytosine, creating 5-methylcytosine that recruits methyl-CpG-
binding domain proteins (MBDs), which in turn attract histone deacetylases and chromatin
remodeling complexes, resulting in condensed heterochromatin structure that prevents
transcription factor access and permanently silences tumor suppressor genes such as MLH1,
BRCA1, and p16INK4a in oncogenesis.
Question 5
In the pathogenesis of Parkinson disease, which mechanism of mitochondrial dysfunction
involves impaired complex I activity leading to increased electron leak and oxidative stress,
particularly affecting dopaminergic neurons of the substantia nigra?
A. Defective mitophagy due to PINK1/Parkin pathway mutations
B. Inhibition of mitochondrial complex I by environmental toxins (e.g., MPTP, rotenone)
C. Mutations in nuclear-encoded mitochondrial proteins
D. All of the above contribute to complex I dysfunction
Correct Answer: D
Rationale: Complex I (NADH dehydrogenase) dysfunction in Parkinson disease results from
multiple convergent mechanisms: (1) autosomal recessive mutations in PINK1 or Parkin impair
mitophagy, allowing accumulation of damaged mitochondria with defective complex I; (2)
environmental toxins like MPTP (metabolized to MPP+) and rotenone specifically inhibit
complex I, causing selective nigrostriatal degeneration; and (3) mutations in nuclear genes
encoding mitochondrial proteins disrupt oxidative phosphorylation. All pathways increase
reactive oxygen species production from electron leak, overwhelm antioxidant defenses, and
trigger neuronal death.
Question 6
A patient with cystic fibrosis has a mutation resulting in ΔF508 in the CFTR protein. What is the
primary cellular pathophysiology responsible for the disease manifestations?
A. Complete absence of CFTR protein synthesis
B. Misfolded protein retained in endoplasmic reticulum with defective processing and trafficking
to cell membrane
C. Normal trafficking but defective chloride channel gating at the apical membrane
D. Accelerated protein degradation by the proteasome system
, 4
Correct Answer: B
Rationale: The ΔF508 mutation deletes phenylalanine at position 508, causing CFTR protein
misfolding during synthesis in the endoplasmic reticulum. Quality control mechanisms recognize
the misfolded protein, retaining it in the ER via chaperone interactions (calnexin cycle),
preventing Golgi processing and trafficking to the apical epithelial membrane. The minimal
protein that escapes degradation exhibits defective chloride conductance and reduced half-life,
resulting in absent chloride secretion, sodium hyperabsorption, dehydrated mucus, and
downstream obstructive lung disease and pancreatic insufficiency.
Question 7
Which mechanism best explains the phenomenon of genomic imprinting disorders such as
Prader-Willi syndrome when inherited paternally versus Angelman syndrome when the same
chromosomal region is deleted maternally?
A. X-inactivation via Xist RNA coating
B. Parent-of-origin-specific DNA methylation silencing one allele
C. Trinucleotide repeat expansion instability
D. Mitochondrial inheritance patterns
Correct Answer: B
Rationale: Genomic imprinting involves parent-of-origin-specific epigenetic marks established
during gametogenesis. At 15q11-q13, the paternal allele expresses SNRPN and other genes while
the maternal allele is silenced via promoter methylation; conversely, the maternal allele
expresses UBE3A while the paternal allele is silenced. Paternal deletion causes Prader-Willi
syndrome (absent paternal genes), while maternal deletion causes Angelman syndrome (absent
UBE3A). This demonstrates that DNA methylation patterns determine allele-specific silencing
based on parental origin, not DNA sequence differences.
Question 8
In reperfusion injury following myocardial infarction, which reactive oxygen species generation
mechanism predominates when oxygen is reintroduced to ischemic tissue?
A. Uncoupled nitric oxide synthase
B. Xanthine oxidase conversion during hypoxanthine accumulation
C. Mitochondrial electron transport chain with impaired complex III
D. NADPH oxidase activation in neutrophils
Correct Answer: C
NR507 / NR 507 Midterm ACTUAL EXAM
2026/2027 | Advanced Pathophysiology | Verified
Questions and Answers 100% Correct | Grade A |
Chamberlain | Pass Guaranteed
Section 1: Cellular & Genetic Mechanisms of Disease (Questions 1-20)
Question 1
A 35-year-old patient presents with neurodegenerative symptoms and progressive myoclonic
epilepsy. Genetic testing reveals an expansion of a trinucleotide repeat (CAG) on chromosome 4.
Which molecular mechanism best explains the pathogenesis of this disorder?
A. Methylation-induced gene silencing
B. Gain-of-function toxicity from expanded polyglutamine tract
C. Loss of tumor suppressor function
D. Genomic imprinting with maternal uniparental disomy
Correct Answer: B
Rationale: The CAG trinucleotide repeat expansion on chromosome 4 characterizes Huntington
disease, where the expanded polyglutamine tract in the huntingtin protein confers a toxic gain-of-
function. The mutant protein misfolds, aggregates in neuronal nuclei and cytoplasm, disrupts
proteasome function, impairs mitochondrial dynamics, and interferes with transcriptional
regulation, leading to striatal neuronal death through multiple downstream mechanisms including
excitotoxicity and altered gene expression.
Question 2
In acute cellular injury, which intracellular event represents the "point of no return" marking
irreversible injury before morphological evidence of necrosis becomes visible?
A. Depletion of ATP stores
B. Influx of calcium ions and activation of phospholipases
C. Loss of mitochondrial membrane potential and inability to reverse mitochondrial permeability
transition pore (mPTP) opening
D. Accumulation of reactive oxygen species
,2
Correct Answer: C
Rationale: The opening of the mitochondrial permeability transition pore (mPTP) represents the
critical irreversible step in cell injury. Once the mPTP opens persistently, mitochondrial
membrane potential collapses, oxidative phosphorylation ceases permanently, cytochrome c and
other pro-apoptotic factors leak into the cytosol, and cellular energy metabolism cannot be
restored regardless of reperfusion or removal of the injurious stimulus, committing the cell to
death.
Question 3
A researcher observes that exposure to hypoxia induces programmed cell death in myocardial
cells characterized by cell shrinkage, chromatin condensation, membrane blebbing, and
formation of apoptotic bodies without inflammation. Which caspase activation pathway is
primarily responsible for initiating this process in response to hypoxic injury?
A. Extrinsic pathway via Fas/Fas ligand interaction
B. Intrinsic (mitochondrial) pathway via Bcl-2 family protein modulation and cytochrome c
release
C. Inflammatory caspase pathway via NLRP3 inflammasome
D. Granzyme B-mediated pathway
Correct Answer: B
Rationale: Hypoxia-induced apoptosis in cardiomyocytes primarily occurs through the intrinsic
mitochondrial pathway. Hypoxia triggers Bcl-2 family protein dysregulation with increased
Bax/Bak oligomerization and decreased Bcl-2/Bcl-xL anti-apoptotic function, causing
mitochondrial outer membrane permeabilization, cytochrome c release into cytosol, apoptosome
formation with Apaf-1, and sequential activation of initiator caspase-9 followed by executioner
caspases-3 and -7, culminating in the characteristic apoptotic morphology.
Question 4
Which epigenetic modification involves the addition of methyl groups to cytosine residues in
CpG islands, typically resulting in long-term transcriptional silencing of tumor suppressor genes
in cancer pathogenesis?
A. Histone acetylation
B. DNA methylation
C. Histone methylation at H3K4me3
D. Chromatin remodeling via SWI/SNF complex
,3
Correct Answer: B
Rationale: DNA methylation at CpG islands in gene promoter regions represents the primary
epigenetic mechanism for stable gene silencing. DNA methyltransferases (DNMTs) catalyze the
addition of methyl groups to cytosine, creating 5-methylcytosine that recruits methyl-CpG-
binding domain proteins (MBDs), which in turn attract histone deacetylases and chromatin
remodeling complexes, resulting in condensed heterochromatin structure that prevents
transcription factor access and permanently silences tumor suppressor genes such as MLH1,
BRCA1, and p16INK4a in oncogenesis.
Question 5
In the pathogenesis of Parkinson disease, which mechanism of mitochondrial dysfunction
involves impaired complex I activity leading to increased electron leak and oxidative stress,
particularly affecting dopaminergic neurons of the substantia nigra?
A. Defective mitophagy due to PINK1/Parkin pathway mutations
B. Inhibition of mitochondrial complex I by environmental toxins (e.g., MPTP, rotenone)
C. Mutations in nuclear-encoded mitochondrial proteins
D. All of the above contribute to complex I dysfunction
Correct Answer: D
Rationale: Complex I (NADH dehydrogenase) dysfunction in Parkinson disease results from
multiple convergent mechanisms: (1) autosomal recessive mutations in PINK1 or Parkin impair
mitophagy, allowing accumulation of damaged mitochondria with defective complex I; (2)
environmental toxins like MPTP (metabolized to MPP+) and rotenone specifically inhibit
complex I, causing selective nigrostriatal degeneration; and (3) mutations in nuclear genes
encoding mitochondrial proteins disrupt oxidative phosphorylation. All pathways increase
reactive oxygen species production from electron leak, overwhelm antioxidant defenses, and
trigger neuronal death.
Question 6
A patient with cystic fibrosis has a mutation resulting in ΔF508 in the CFTR protein. What is the
primary cellular pathophysiology responsible for the disease manifestations?
A. Complete absence of CFTR protein synthesis
B. Misfolded protein retained in endoplasmic reticulum with defective processing and trafficking
to cell membrane
C. Normal trafficking but defective chloride channel gating at the apical membrane
D. Accelerated protein degradation by the proteasome system
, 4
Correct Answer: B
Rationale: The ΔF508 mutation deletes phenylalanine at position 508, causing CFTR protein
misfolding during synthesis in the endoplasmic reticulum. Quality control mechanisms recognize
the misfolded protein, retaining it in the ER via chaperone interactions (calnexin cycle),
preventing Golgi processing and trafficking to the apical epithelial membrane. The minimal
protein that escapes degradation exhibits defective chloride conductance and reduced half-life,
resulting in absent chloride secretion, sodium hyperabsorption, dehydrated mucus, and
downstream obstructive lung disease and pancreatic insufficiency.
Question 7
Which mechanism best explains the phenomenon of genomic imprinting disorders such as
Prader-Willi syndrome when inherited paternally versus Angelman syndrome when the same
chromosomal region is deleted maternally?
A. X-inactivation via Xist RNA coating
B. Parent-of-origin-specific DNA methylation silencing one allele
C. Trinucleotide repeat expansion instability
D. Mitochondrial inheritance patterns
Correct Answer: B
Rationale: Genomic imprinting involves parent-of-origin-specific epigenetic marks established
during gametogenesis. At 15q11-q13, the paternal allele expresses SNRPN and other genes while
the maternal allele is silenced via promoter methylation; conversely, the maternal allele
expresses UBE3A while the paternal allele is silenced. Paternal deletion causes Prader-Willi
syndrome (absent paternal genes), while maternal deletion causes Angelman syndrome (absent
UBE3A). This demonstrates that DNA methylation patterns determine allele-specific silencing
based on parental origin, not DNA sequence differences.
Question 8
In reperfusion injury following myocardial infarction, which reactive oxygen species generation
mechanism predominates when oxygen is reintroduced to ischemic tissue?
A. Uncoupled nitric oxide synthase
B. Xanthine oxidase conversion during hypoxanthine accumulation
C. Mitochondrial electron transport chain with impaired complex III
D. NADPH oxidase activation in neutrophils
Correct Answer: C
