WGU D236 Pathophysiology Objective Assessment Exam
Question Bank (Latest 2026/2027 Edition) – Questions,
Answers & Detailed Rationales
──────────────────────────────
SECTION 1: CELLULAR PATHOPHYSIOLOGY AND GENETICS
──────────────────────────────
Question 1
A 45-year-old male presents with progressive muscle weakness, exercise intolerance,
and lactic acidosis. Muscle biopsy reveals ragged-red fibers. Genetic testing identifies a
mutation in mitochondrial DNA. Which pathophysiologic mechanism best explains the
inheritance pattern and tissue specificity of this disorder?
A. Autosomal dominant inheritance with variable penetrance affecting all tissues
equally
B. Maternal inheritance with heteroplasmy causing variable expression in tissues with
high metabolic demand
C. X-linked recessive inheritance with lyonization producing mosaic tissue effects
D. Autosomal recessive inheritance with complete loss of function in all mitochondria
Correct Answer:
B — Maternal inheritance with heteroplasmy causing variable expression in tissues with
high metabolic demand
Rationale:
Mitochondrial DNA is inherited exclusively from the mother. Heteroplasmy (mixture of
mutant and normal mitochondria) results in variable expression depending on the
proportion of mutant mitochondria in each cell. Tissues with high oxidative
phosphorylation requirements (muscle, brain, heart) are most affected. Autosomal and
X-linked patterns do not apply to mitochondrial DNA inheritance.
,Question 2
A 28-year-old female develops bilateral breast cancer. Her mother had ovarian cancer at
age 42, and her maternal aunt had breast cancer at age 38. Genetic testing reveals a
BRCA1 mutation. Which cellular mechanism explains the increased cancer risk?
A. Defective mismatch repair leading to microsatellite instability
B. Impaired homologous recombination repair of double-strand DNA breaks
C. Activated tyrosine kinase signaling driving uncontrolled proliferation
D. Loss of cell cycle checkpoint control at the G1/S transition
Correct Answer:
B — Impaired homologous recombination repair of double-strand DNA breaks
Rationale:
BRCA1 and BRCA2 are tumor suppressor genes involved in homologous recombination
repair of double-strand DNA breaks. Mutations result in genomic instability and
increased susceptibility to breast, ovarian, and other cancers. Mismatch repair defects
cause Lynch syndrome (MLH1, MSH2). Tyrosine kinase activation characterizes
oncogene-driven cancers. G1/S checkpoint loss involves p53 or RB pathways.
Question 3
A 6-year-old male presents with recurrent infections, eczema, and thrombocytopenia.
Laboratory studies reveal low IgM and elevated IgA/IgE. Genetic testing confirms
Wiskott-Aldrich syndrome. Which cellular defect is responsible?
A. Defective B-cell receptor signaling due to Bruton tyrosine kinase mutation
B. Impaired actin cytoskeleton reorganization in hematopoietic cells due to WAS protein
mutation
C. Defective T-cell receptor V(D)J recombination due to RAG1/RAG2 mutation
D. Abnormal neutrophil respiratory burst due to NADPH oxidase deficiency
Correct Answer:
,B — Impaired actin cytoskeleton reorganization in hematopoietic cells due to WAS
protein mutation
Rationale:
Wiskott-Aldrich syndrome results from mutations in the WAS gene encoding
Wiskott-Aldrich syndrome protein, which regulates actin cytoskeleton reorganization in
hematopoietic cells. This affects T-cell function, platelet production, and B-cell
responses. Bruton tyrosine kinase mutations cause X-linked agammaglobulinemia. RAG
mutations cause severe combined immunodeficiency. NADPH oxidase deficiency
causes chronic granulomatous disease.
Question 4
A 55-year-old male with chronic sun exposure develops a non-healing ulcerated skin
lesion on his forearm. Biopsy reveals atypical keratinocytes with intercellular bridges
invading the dermis. Which pathophysiologic process is most likely responsible?
A. UV-induced p53 mutations leading to uncontrolled keratinocyte proliferation
B. HPV E6/E7 oncoprotein-driven degradation of Rb and p53
C. Chronic arsenic exposure activating the Hedgehog signaling pathway
D. Immunosuppression permitting Merkel cell polyomavirus replication
Correct Answer:
A — UV-induced p53 mutations leading to uncontrolled keratinocyte proliferation
Rationale:
Squamous cell carcinoma, characterized by invasive atypical keratinocytes with
intercellular bridges, is strongly associated with UV-induced p53 mutations. UV radiation
causes pyrimidine dimers and p53 mutations that impair apoptosis and cell cycle
control. HPV drives cervical and oropharyngeal SCC. Arsenic and Hedgehog pathways
are associated with basal cell carcinoma. Merkel cell polyomavirus causes Merkel cell
carcinoma.
, Question 5
A 32-year-old female presents with progressive dyspnea, hemoptysis, and
glomerulonephritis. Renal biopsy shows linear IgG deposition along the glomerular
basement membrane. Which autoantigen is targeted in this disease?
A. Type IV collagen alpha-3 chain (Goodpasture antigen)
B. Double-stranded DNA
C. Smith antigen
D. Myeloperoxidase
Correct Answer:
A — Type IV collagen alpha-3 chain (Goodpasture antigen)
Rationale:
Goodpasture syndrome (anti-GBM disease) is characterized by autoantibodies against
the non-collagenous domain of type IV collagen alpha-3 chain, causing linear IgG
deposition on immunofluorescence and simultaneous pulmonary hemorrhage and
glomerulonephritis. Anti-dsDNA and Smith antibodies are specific for systemic lupus
erythematosus. Anti-myeloperoxidase (p-ANCA) is associated with microscopic
polyangiitis.
──────────────────────────────
SECTION 2: CARDIOVASCULAR PATHOPHYSIOLOGY
──────────────────────────────
Question 6
A 62-year-old male with hypertension presents with crushing substernal chest pain
radiating to his left arm. ECG shows ST-elevation in leads V1-V4. Troponin I is elevated.
Coronary angiography reveals 95% stenosis of the left anterior descending artery with
thrombus. Which pathophysiologic sequence initiated this acute coronary syndrome?
Question Bank (Latest 2026/2027 Edition) – Questions,
Answers & Detailed Rationales
──────────────────────────────
SECTION 1: CELLULAR PATHOPHYSIOLOGY AND GENETICS
──────────────────────────────
Question 1
A 45-year-old male presents with progressive muscle weakness, exercise intolerance,
and lactic acidosis. Muscle biopsy reveals ragged-red fibers. Genetic testing identifies a
mutation in mitochondrial DNA. Which pathophysiologic mechanism best explains the
inheritance pattern and tissue specificity of this disorder?
A. Autosomal dominant inheritance with variable penetrance affecting all tissues
equally
B. Maternal inheritance with heteroplasmy causing variable expression in tissues with
high metabolic demand
C. X-linked recessive inheritance with lyonization producing mosaic tissue effects
D. Autosomal recessive inheritance with complete loss of function in all mitochondria
Correct Answer:
B — Maternal inheritance with heteroplasmy causing variable expression in tissues with
high metabolic demand
Rationale:
Mitochondrial DNA is inherited exclusively from the mother. Heteroplasmy (mixture of
mutant and normal mitochondria) results in variable expression depending on the
proportion of mutant mitochondria in each cell. Tissues with high oxidative
phosphorylation requirements (muscle, brain, heart) are most affected. Autosomal and
X-linked patterns do not apply to mitochondrial DNA inheritance.
,Question 2
A 28-year-old female develops bilateral breast cancer. Her mother had ovarian cancer at
age 42, and her maternal aunt had breast cancer at age 38. Genetic testing reveals a
BRCA1 mutation. Which cellular mechanism explains the increased cancer risk?
A. Defective mismatch repair leading to microsatellite instability
B. Impaired homologous recombination repair of double-strand DNA breaks
C. Activated tyrosine kinase signaling driving uncontrolled proliferation
D. Loss of cell cycle checkpoint control at the G1/S transition
Correct Answer:
B — Impaired homologous recombination repair of double-strand DNA breaks
Rationale:
BRCA1 and BRCA2 are tumor suppressor genes involved in homologous recombination
repair of double-strand DNA breaks. Mutations result in genomic instability and
increased susceptibility to breast, ovarian, and other cancers. Mismatch repair defects
cause Lynch syndrome (MLH1, MSH2). Tyrosine kinase activation characterizes
oncogene-driven cancers. G1/S checkpoint loss involves p53 or RB pathways.
Question 3
A 6-year-old male presents with recurrent infections, eczema, and thrombocytopenia.
Laboratory studies reveal low IgM and elevated IgA/IgE. Genetic testing confirms
Wiskott-Aldrich syndrome. Which cellular defect is responsible?
A. Defective B-cell receptor signaling due to Bruton tyrosine kinase mutation
B. Impaired actin cytoskeleton reorganization in hematopoietic cells due to WAS protein
mutation
C. Defective T-cell receptor V(D)J recombination due to RAG1/RAG2 mutation
D. Abnormal neutrophil respiratory burst due to NADPH oxidase deficiency
Correct Answer:
,B — Impaired actin cytoskeleton reorganization in hematopoietic cells due to WAS
protein mutation
Rationale:
Wiskott-Aldrich syndrome results from mutations in the WAS gene encoding
Wiskott-Aldrich syndrome protein, which regulates actin cytoskeleton reorganization in
hematopoietic cells. This affects T-cell function, platelet production, and B-cell
responses. Bruton tyrosine kinase mutations cause X-linked agammaglobulinemia. RAG
mutations cause severe combined immunodeficiency. NADPH oxidase deficiency
causes chronic granulomatous disease.
Question 4
A 55-year-old male with chronic sun exposure develops a non-healing ulcerated skin
lesion on his forearm. Biopsy reveals atypical keratinocytes with intercellular bridges
invading the dermis. Which pathophysiologic process is most likely responsible?
A. UV-induced p53 mutations leading to uncontrolled keratinocyte proliferation
B. HPV E6/E7 oncoprotein-driven degradation of Rb and p53
C. Chronic arsenic exposure activating the Hedgehog signaling pathway
D. Immunosuppression permitting Merkel cell polyomavirus replication
Correct Answer:
A — UV-induced p53 mutations leading to uncontrolled keratinocyte proliferation
Rationale:
Squamous cell carcinoma, characterized by invasive atypical keratinocytes with
intercellular bridges, is strongly associated with UV-induced p53 mutations. UV radiation
causes pyrimidine dimers and p53 mutations that impair apoptosis and cell cycle
control. HPV drives cervical and oropharyngeal SCC. Arsenic and Hedgehog pathways
are associated with basal cell carcinoma. Merkel cell polyomavirus causes Merkel cell
carcinoma.
, Question 5
A 32-year-old female presents with progressive dyspnea, hemoptysis, and
glomerulonephritis. Renal biopsy shows linear IgG deposition along the glomerular
basement membrane. Which autoantigen is targeted in this disease?
A. Type IV collagen alpha-3 chain (Goodpasture antigen)
B. Double-stranded DNA
C. Smith antigen
D. Myeloperoxidase
Correct Answer:
A — Type IV collagen alpha-3 chain (Goodpasture antigen)
Rationale:
Goodpasture syndrome (anti-GBM disease) is characterized by autoantibodies against
the non-collagenous domain of type IV collagen alpha-3 chain, causing linear IgG
deposition on immunofluorescence and simultaneous pulmonary hemorrhage and
glomerulonephritis. Anti-dsDNA and Smith antibodies are specific for systemic lupus
erythematosus. Anti-myeloperoxidase (p-ANCA) is associated with microscopic
polyangiitis.
──────────────────────────────
SECTION 2: CARDIOVASCULAR PATHOPHYSIOLOGY
──────────────────────────────
Question 6
A 62-year-old male with hypertension presents with crushing substernal chest pain
radiating to his left arm. ECG shows ST-elevation in leads V1-V4. Troponin I is elevated.
Coronary angiography reveals 95% stenosis of the left anterior descending artery with
thrombus. Which pathophysiologic sequence initiated this acute coronary syndrome?
