NR 507 Advanced Pathophysiology Midterm
Exam Official Practice Exam Actual Exam
2026/2027 with Detailed Rationales |
Complete Exam-Style Questions | Pass
Guaranteed – A+ Graded
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SECTION 1: CELLULAR BIOLOGY & GENETICS Q1 – Q10
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Question 1 of 50
A 42-year-old woman with a known BRCA1 gene mutation undergoes prophylactic bilateral
mastectomy. During genetic counseling, she asks why this mutation predisposes her to
breast cancer. The pathophysiologic mechanism involves which cellular process?
A. Activation of proto-oncogenes leading to uncontrolled cellular proliferation
B. Enhanced telomerase activity preventing normal cellular senescence
C. Loss of DNA repair capability and genomic instability in breast epithelial cells ✓ CORRECT
D. Overexpression of growth factor receptors on mammary cell membranes
Correct Answer: C
Rationale: BRCA1 functions as a tumor suppressor gene that encodes a protein essential for
homologous recombination repair of DNA double-strand breaks; mutation leads to genomic
instability and carcinogenesis. Proto-oncogene activation describes a different mechanism
seen in cancers driven by oncogenes such as HER2/neu amplification, not BRCA1-related
tumorigenesis. Understanding tumor suppressor versus oncogene mechanisms is essential
for distinguishing hereditary cancer syndromes on the exam.
Question 2 of 50
A 6-month-old infant presents with failure to thrive, steatorrhea, and a salty taste to the skin.
Sweat chloride testing confirms a concentration of 92 mmol/L. The underlying
pathophysiology reflects which molecular defect?
A. Defective chloride ion transport across epithelial cell membranes due to CFTR mutation ✓
CORRECT
B. Excessive sodium reabsorption in the distal convoluted tubule of the kidney
,C. Impaired bile acid synthesis within hepatocytes causing fat malabsorption
D. Pancreatic duct obstruction by inspissated mucus plugs alone
Correct Answer: A
Rationale: Cystic fibrosis results from mutations in the CFTR gene that encodes a chloride
channel, leading to defective ion transport and thick secretions in multiple organs. While
pancreatic duct obstruction does occur, it is a secondary consequence of the primary
epithelial chloride channel defect rather than the root cause. Remember that CFTR
dysfunction is the primary molecular abnormality; all other manifestations are downstream
effects.
Question 3 of 50
A 28-year-old African American man with sickle cell disease presents with severe pain in his
legs and back. Laboratory studies reveal a hemoglobin of 6.8 g/dL and elevated reticulocyte
count. The vaso-occlusive crisis is initiated by which pathophysiologic event?
A. Autoimmune hemolysis triggered by cold-reactive IgM antibodies
B. Bone marrow suppression from parvovirus B19 infection
C. Increased oxygen affinity of mutated hemoglobin molecules
D. Polymerization of deoxygenated hemoglobin S into insoluble fibers ✓ CORRECT
Correct Answer: D
Rationale: Under low oxygen tension, hemoglobin S polymerizes into rigid fibers that distort
erythrocytes into a sickle shape, causing hemolysis and vaso-occlusion. Autoimmune
hemolysis describes cold agglutinin disease, which is unrelated to the molecular
pathophysiology of sickle cell disease. Focus on the central role of hemoglobin S
polymerization as the initiating event in all sickle cell crises.
Question 4 of 50
A 55-year-old man with a 40 pack-year smoking history develops a non-small cell lung
carcinoma. Molecular analysis reveals a KRAS mutation. Which pathophysiologic mechanism
best explains the role of this mutation in his cancer development?
A. Inactivation of a DNA repair enzyme leading to accumulation of mutations
B. Constitutive activation of a GTPase signaling protein driving continuous cellular
proliferation ✓ CORRECT
C. Loss of cell cycle checkpoint control through p53 pathway disruption
D. Enhanced apoptosis resistance via overexpression of BCL-2 proteins
Correct Answer: B
Rationale: KRAS is a proto-oncogene that encodes a GTPase involved in growth factor
signaling; mutation causes constitutive activation and uncontrolled downstream MAPK/ERK
, proliferation signals. DNA repair enzyme inactivation describes tumor suppressor
mechanisms such as BRCA1 or mismatch repair defects, not oncogene activation.
Distinguishing oncogenes that promote proliferation from tumor suppressors that restrain
growth is fundamental to understanding cancer pathophysiology.
Question 5 of 50
A 35-year-old woman gives birth to a child with Down syndrome. Karyotype analysis reveals
trisomy 21. Which cellular event during gametogenesis is the most common cause of this
chromosomal abnormality?
A. Translocation of genetic material between nonhomologous chromosomes
B. Chromosomal deletion during the S phase of mitosis
C. Nondisjunction of homologous chromosomes during maternal meiosis I ✓ CORRECT
D. Random chromosomal loss during early embryonic cleavage
Correct Answer: C
Rationale: Approximately 95% of Down syndrome cases result from meiotic nondisjunction,
with maternal meiosis I errors accounting for the majority due to the prolonged arrest of
oocytes. Translocation Down syndrome occurs in only about 4% of cases and typically
involves Robertsonian translocation. Recognize that nondisjunction is the predominant
mechanism for trisomy 21, while translocation is a less common but important alternative.
Question 6 of 50
A 38-year-old man presents with progressive chorea, cognitive decline, and psychiatric
symptoms. His father had similar symptoms beginning at age 45. Genetic testing reveals an
expanded CAG trinucleotide repeat on chromosome 4. Which molecular mechanism
underlies neuronal death in this disorder?
A. Toxic gain-of-function from an expanded polyglutamine tract in the huntingtin protein ✓
CORRECT
B. Loss of function in the ubiquitin-proteasome degradation pathway
C. Defective mitochondrial DNA replication causing energy failure
D. Abnormal cholesterol synthesis disrupting neuronal membrane integrity
Correct Answer: A
Rationale: Huntington disease results from CAG repeat expansion in the HTT gene, producing
a mutant huntingtin protein with an elongated polyglutamine tract that accumulates
intracellularly and causes neuronal toxicity. Loss of ubiquitin-proteasome function is a
downstream effect of protein aggregation rather than the primary genetic defect. Note that
trinucleotide repeat disorders involve toxic gain-of-function, distinguishing them from
loss-of-function metabolic disorders.
Exam Official Practice Exam Actual Exam
2026/2027 with Detailed Rationales |
Complete Exam-Style Questions | Pass
Guaranteed – A+ Graded
══════════════════════════════════════
SECTION 1: CELLULAR BIOLOGY & GENETICS Q1 – Q10
══════════════════════════════════════
Question 1 of 50
A 42-year-old woman with a known BRCA1 gene mutation undergoes prophylactic bilateral
mastectomy. During genetic counseling, she asks why this mutation predisposes her to
breast cancer. The pathophysiologic mechanism involves which cellular process?
A. Activation of proto-oncogenes leading to uncontrolled cellular proliferation
B. Enhanced telomerase activity preventing normal cellular senescence
C. Loss of DNA repair capability and genomic instability in breast epithelial cells ✓ CORRECT
D. Overexpression of growth factor receptors on mammary cell membranes
Correct Answer: C
Rationale: BRCA1 functions as a tumor suppressor gene that encodes a protein essential for
homologous recombination repair of DNA double-strand breaks; mutation leads to genomic
instability and carcinogenesis. Proto-oncogene activation describes a different mechanism
seen in cancers driven by oncogenes such as HER2/neu amplification, not BRCA1-related
tumorigenesis. Understanding tumor suppressor versus oncogene mechanisms is essential
for distinguishing hereditary cancer syndromes on the exam.
Question 2 of 50
A 6-month-old infant presents with failure to thrive, steatorrhea, and a salty taste to the skin.
Sweat chloride testing confirms a concentration of 92 mmol/L. The underlying
pathophysiology reflects which molecular defect?
A. Defective chloride ion transport across epithelial cell membranes due to CFTR mutation ✓
CORRECT
B. Excessive sodium reabsorption in the distal convoluted tubule of the kidney
,C. Impaired bile acid synthesis within hepatocytes causing fat malabsorption
D. Pancreatic duct obstruction by inspissated mucus plugs alone
Correct Answer: A
Rationale: Cystic fibrosis results from mutations in the CFTR gene that encodes a chloride
channel, leading to defective ion transport and thick secretions in multiple organs. While
pancreatic duct obstruction does occur, it is a secondary consequence of the primary
epithelial chloride channel defect rather than the root cause. Remember that CFTR
dysfunction is the primary molecular abnormality; all other manifestations are downstream
effects.
Question 3 of 50
A 28-year-old African American man with sickle cell disease presents with severe pain in his
legs and back. Laboratory studies reveal a hemoglobin of 6.8 g/dL and elevated reticulocyte
count. The vaso-occlusive crisis is initiated by which pathophysiologic event?
A. Autoimmune hemolysis triggered by cold-reactive IgM antibodies
B. Bone marrow suppression from parvovirus B19 infection
C. Increased oxygen affinity of mutated hemoglobin molecules
D. Polymerization of deoxygenated hemoglobin S into insoluble fibers ✓ CORRECT
Correct Answer: D
Rationale: Under low oxygen tension, hemoglobin S polymerizes into rigid fibers that distort
erythrocytes into a sickle shape, causing hemolysis and vaso-occlusion. Autoimmune
hemolysis describes cold agglutinin disease, which is unrelated to the molecular
pathophysiology of sickle cell disease. Focus on the central role of hemoglobin S
polymerization as the initiating event in all sickle cell crises.
Question 4 of 50
A 55-year-old man with a 40 pack-year smoking history develops a non-small cell lung
carcinoma. Molecular analysis reveals a KRAS mutation. Which pathophysiologic mechanism
best explains the role of this mutation in his cancer development?
A. Inactivation of a DNA repair enzyme leading to accumulation of mutations
B. Constitutive activation of a GTPase signaling protein driving continuous cellular
proliferation ✓ CORRECT
C. Loss of cell cycle checkpoint control through p53 pathway disruption
D. Enhanced apoptosis resistance via overexpression of BCL-2 proteins
Correct Answer: B
Rationale: KRAS is a proto-oncogene that encodes a GTPase involved in growth factor
signaling; mutation causes constitutive activation and uncontrolled downstream MAPK/ERK
, proliferation signals. DNA repair enzyme inactivation describes tumor suppressor
mechanisms such as BRCA1 or mismatch repair defects, not oncogene activation.
Distinguishing oncogenes that promote proliferation from tumor suppressors that restrain
growth is fundamental to understanding cancer pathophysiology.
Question 5 of 50
A 35-year-old woman gives birth to a child with Down syndrome. Karyotype analysis reveals
trisomy 21. Which cellular event during gametogenesis is the most common cause of this
chromosomal abnormality?
A. Translocation of genetic material between nonhomologous chromosomes
B. Chromosomal deletion during the S phase of mitosis
C. Nondisjunction of homologous chromosomes during maternal meiosis I ✓ CORRECT
D. Random chromosomal loss during early embryonic cleavage
Correct Answer: C
Rationale: Approximately 95% of Down syndrome cases result from meiotic nondisjunction,
with maternal meiosis I errors accounting for the majority due to the prolonged arrest of
oocytes. Translocation Down syndrome occurs in only about 4% of cases and typically
involves Robertsonian translocation. Recognize that nondisjunction is the predominant
mechanism for trisomy 21, while translocation is a less common but important alternative.
Question 6 of 50
A 38-year-old man presents with progressive chorea, cognitive decline, and psychiatric
symptoms. His father had similar symptoms beginning at age 45. Genetic testing reveals an
expanded CAG trinucleotide repeat on chromosome 4. Which molecular mechanism
underlies neuronal death in this disorder?
A. Toxic gain-of-function from an expanded polyglutamine tract in the huntingtin protein ✓
CORRECT
B. Loss of function in the ubiquitin-proteasome degradation pathway
C. Defective mitochondrial DNA replication causing energy failure
D. Abnormal cholesterol synthesis disrupting neuronal membrane integrity
Correct Answer: A
Rationale: Huntington disease results from CAG repeat expansion in the HTT gene, producing
a mutant huntingtin protein with an elongated polyglutamine tract that accumulates
intracellularly and causes neuronal toxicity. Loss of ubiquitin-proteasome function is a
downstream effect of protein aggregation rather than the primary genetic defect. Note that
trinucleotide repeat disorders involve toxic gain-of-function, distinguishing them from
loss-of-function metabolic disorders.
