NR507NP ACTUAL EXAM 2026/2027 |
Advanced Pathophysiology | Verified Q&A |
Pass Guaranteed - A+ Graded
Section 1: Cellular Biology & Genetics (Q1–Q8)
Q1: A 34-year-old woman presents with progressive muscle weakness, exercise intolerance, and
elevated serum lactate. Muscle biopsy reveals ragged-red fibers. Which pathophysiologic process best
explains the cellular mechanism underlying this disorder?
A. Defective lysosomal enzyme leading to substrate accumulation in cytoplasmic vacuoles
B. Impaired oxidative phosphorylation due to mitochondrial DNA mutation [CORRECT]
C. Abnormal microtubule polymerization causing disrupted intracellular transport
D. Excessive peroxisomal proliferation resulting in reactive oxygen species overproduction
Correct Answer: B
Rationale: Ragged-red fibers on muscle biopsy are pathognomonic for mitochondrial myopathies, which
result from mutations in mitochondrial DNA encoding components of the electron transport chain. This
impairs oxidative phosphorylation, leading to insufficient ATP production, lactic acid accumulation from
anaerobic metabolism, and the characteristic ragged appearance due to subsarcolemmal mitochondrial
proliferation.
Q2: A patient with Li-Fraumeni syndrome develops a second primary malignancy. Which genetic
mechanism is primarily responsible for the increased cancer susceptibility in this autosomal dominant
condition?
A. Gain-of-function mutation in a proto-oncogene promoting uncontrolled cellular proliferation
B. Loss-of-function mutation in a tumor suppressor gene [CORRECT]
C. Chromosomal translocation creating a fusion gene with constitutive tyrosine kinase activity
D. Epigenetic hypermethylation of promoter regions leading to global gene silencing
Correct Answer: B
Rationale: Li-Fraumeni syndrome is caused by germline mutations in the TP53 tumor suppressor gene.
Tumor suppressor genes normally regulate cell cycle checkpoints, DNA repair, and apoptosis; loss-of-
,function mutations in both alleles (the "two-hit" hypothesis) remove these regulatory constraints,
allowing malignant transformation. TP53 is the classic example of a tumor suppressor, distinct from
oncogenes which require only one mutated allele for activation.
Q3: A child is born with cystic fibrosis. Both parents are phenotypically healthy. Which inheritance
pattern and molecular mechanism best explain this presentation?
A. Autosomal dominant inheritance with incomplete penetrance due to a missense mutation
B. Autosomal recessive inheritance requiring two mutated CFTR alleles [CORRECT]
C. X-linked recessive inheritance with the mother as an obligatory carrier
D. Mitochondrial inheritance with maternal transmission of the CFTR mutation
Correct Answer: B
Rationale: Cystic fibrosis follows autosomal recessive inheritance, requiring mutations in both CFTR
alleles for disease expression. The CFTR gene encodes a chloride channel; loss-of-function mutations
result in defective chloride transport, leading to thick mucus secretions. Both parents are asymptomatic
carriers (heterozygotes) with one normal and one mutated allele, giving each offspring a 25% chance of
inheriting two mutated alleles.
Q4: In response to chronic hypoxia, a patient's kidneys increase erythropoietin production, stimulating
bone marrow erythropoiesis. This represents which type of cellular adaptation?
A. Hypertrophy
B. Hyperplasia [CORRECT]
C. Metaplasia
D. Dysplasia
Correct Answer: B
Rationale: Hyperplasia is an increase in cell number in response to a stimulus, distinct from hypertrophy
(increase in cell size). Erythropoietin-driven erythropoiesis increases the absolute number of red blood
cells, representing physiologic hyperplasia—a compensatory adaptive response that enhances oxygen-
carrying capacity to meet metabolic demands under hypoxic conditions.
Q5: A 28-year-old man has Huntington disease. His father was affected, but his mother was not. Which
statement accurately describes the genetic mechanism and probability of transmission?
A. X-linked recessive; all daughters will be carriers, no sons affected
B. Autosomal dominant; each child has a 50% risk of inheriting the mutation [CORRECT]
,C. Autosomal recessive; both parents must be carriers for disease expression
D. Mitochondrial inheritance; all offspring inherit the mutation from the father
Correct Answer: B
Rationale: Huntington disease is an autosomal dominant disorder caused by CAG trinucleotide repeat
expansion in the HTT gene. With one affected parent, each offspring has a 50% probability of inheriting
the mutated allele. The disease exhibits complete penetrance, meaning all individuals with the mutation
will eventually manifest symptoms, typically with anticipation (earlier onset in successive generations
due to repeat expansion).
Q6: A biopsy reveals cells with markedly enlarged, hyperchromatic nuclei and a high nuclear-to-
cytoplasmic ratio, but the tissue architecture remains organized. Which cellular process is most likely
occurring?
A. Anaplasia
B. Dysplasia [CORRECT]
C. Metaplasia
D. Hyperplasia
Correct Answer: B
Rationale: Dysplasia is characterized by disordered cellular development with nuclear pleomorphism,
hyperchromatism, and increased nuclear-to-cytoplasmic ratio, while maintaining some tissue
architectural organization. It represents a pre-neoplastic change that may be reversible if the inciting
stimulus is removed. Unlike anaplasia (complete loss of differentiation seen in malignant tumors),
dysplasia retains recognizable tissue structure.
Q7: A patient with chronic gastroesophageal reflux develops Barrett esophagus. Which cellular
adaptation explains the replacement of squamous epithelium with columnar epithelium?
A. Hypertrophy of existing squamous cells
B. Metaplasia [CORRECT]
C. Hyperplasia of basal squamous cells
D. Apoptosis of damaged surface cells
Correct Answer: B
Rationale: Metaplasia is the reversible replacement of one differentiated cell type with another better
suited to withstand an adverse environment. In Barrett esophagus, chronic acid exposure causes
, squamous epithelium to convert to intestinal-type columnar epithelium, which is more acid-resistant.
While adaptive, this change increases risk for dysplasia and adenocarcinoma if the irritant persists.
Q8: A tumor biopsy shows increased expression of the RAS oncogene with constitutively active GTP-
bound signaling. Which molecular mechanism best explains the pathophysiology?
A. Loss of both alleles of a tumor suppressor gene
B. Gain-of-function mutation converting a proto-oncogene to an oncogene [CORRECT]
C. Defective DNA mismatch repair causing microsatellite instability
D. Epigenetic silencing of a cell cycle inhibitor gene
Correct Answer: B
Rationale: The RAS gene family encodes GTPases that transduce growth factor signals. In normal cells,
RAS cycles between active GTP-bound and inactive GDP-bound states. Oncogenic mutations (typically at
codons 12, 13, or 61) lock RAS in the constitutively active GTP-bound state, leading to continuous
downstream signaling through the MAPK/ERK pathway and uncontrolled cellular proliferation. This
represents a gain-of-function mechanism requiring only one mutated allele.
Section 2: Fluid, Electrolyte & Acid-Base Balance (Q9–Q14)
Q9: A patient with severe vomiting develops metabolic alkalosis. Which compensatory mechanism will
the body employ to correct the acid-base disturbance?
A. Hyperventilation to decrease PaCO₂
B. Hypoventilation to increase PaCO₂ *CORRECT+
C. Increased renal bicarbonate excretion
D. Increased renal hydrogen ion excretion
Correct Answer: B
Rationale: In metabolic alkalosis, the primary compensatory mechanism is hypoventilation, which
increases PaCO₂ and adds respiratory acid to partially offset the excess bicarbonate. The respiratory
system responds within minutes to hours, whereas renal compensation (bicarbonate excretion) requires
2–3 days to become fully effective. Hypoventilation is the immediate compensatory response.
Q10: A patient with chronic heart failure is prescribed loop diuretics and develops muscle weakness,
cardiac arrhythmias, and flattened T waves on ECG. Which electrolyte imbalance and underlying
pathophysiologic mechanism best explain these findings?
A. Hyperkalemia due to decreased renal potassium excretion
Advanced Pathophysiology | Verified Q&A |
Pass Guaranteed - A+ Graded
Section 1: Cellular Biology & Genetics (Q1–Q8)
Q1: A 34-year-old woman presents with progressive muscle weakness, exercise intolerance, and
elevated serum lactate. Muscle biopsy reveals ragged-red fibers. Which pathophysiologic process best
explains the cellular mechanism underlying this disorder?
A. Defective lysosomal enzyme leading to substrate accumulation in cytoplasmic vacuoles
B. Impaired oxidative phosphorylation due to mitochondrial DNA mutation [CORRECT]
C. Abnormal microtubule polymerization causing disrupted intracellular transport
D. Excessive peroxisomal proliferation resulting in reactive oxygen species overproduction
Correct Answer: B
Rationale: Ragged-red fibers on muscle biopsy are pathognomonic for mitochondrial myopathies, which
result from mutations in mitochondrial DNA encoding components of the electron transport chain. This
impairs oxidative phosphorylation, leading to insufficient ATP production, lactic acid accumulation from
anaerobic metabolism, and the characteristic ragged appearance due to subsarcolemmal mitochondrial
proliferation.
Q2: A patient with Li-Fraumeni syndrome develops a second primary malignancy. Which genetic
mechanism is primarily responsible for the increased cancer susceptibility in this autosomal dominant
condition?
A. Gain-of-function mutation in a proto-oncogene promoting uncontrolled cellular proliferation
B. Loss-of-function mutation in a tumor suppressor gene [CORRECT]
C. Chromosomal translocation creating a fusion gene with constitutive tyrosine kinase activity
D. Epigenetic hypermethylation of promoter regions leading to global gene silencing
Correct Answer: B
Rationale: Li-Fraumeni syndrome is caused by germline mutations in the TP53 tumor suppressor gene.
Tumor suppressor genes normally regulate cell cycle checkpoints, DNA repair, and apoptosis; loss-of-
,function mutations in both alleles (the "two-hit" hypothesis) remove these regulatory constraints,
allowing malignant transformation. TP53 is the classic example of a tumor suppressor, distinct from
oncogenes which require only one mutated allele for activation.
Q3: A child is born with cystic fibrosis. Both parents are phenotypically healthy. Which inheritance
pattern and molecular mechanism best explain this presentation?
A. Autosomal dominant inheritance with incomplete penetrance due to a missense mutation
B. Autosomal recessive inheritance requiring two mutated CFTR alleles [CORRECT]
C. X-linked recessive inheritance with the mother as an obligatory carrier
D. Mitochondrial inheritance with maternal transmission of the CFTR mutation
Correct Answer: B
Rationale: Cystic fibrosis follows autosomal recessive inheritance, requiring mutations in both CFTR
alleles for disease expression. The CFTR gene encodes a chloride channel; loss-of-function mutations
result in defective chloride transport, leading to thick mucus secretions. Both parents are asymptomatic
carriers (heterozygotes) with one normal and one mutated allele, giving each offspring a 25% chance of
inheriting two mutated alleles.
Q4: In response to chronic hypoxia, a patient's kidneys increase erythropoietin production, stimulating
bone marrow erythropoiesis. This represents which type of cellular adaptation?
A. Hypertrophy
B. Hyperplasia [CORRECT]
C. Metaplasia
D. Dysplasia
Correct Answer: B
Rationale: Hyperplasia is an increase in cell number in response to a stimulus, distinct from hypertrophy
(increase in cell size). Erythropoietin-driven erythropoiesis increases the absolute number of red blood
cells, representing physiologic hyperplasia—a compensatory adaptive response that enhances oxygen-
carrying capacity to meet metabolic demands under hypoxic conditions.
Q5: A 28-year-old man has Huntington disease. His father was affected, but his mother was not. Which
statement accurately describes the genetic mechanism and probability of transmission?
A. X-linked recessive; all daughters will be carriers, no sons affected
B. Autosomal dominant; each child has a 50% risk of inheriting the mutation [CORRECT]
,C. Autosomal recessive; both parents must be carriers for disease expression
D. Mitochondrial inheritance; all offspring inherit the mutation from the father
Correct Answer: B
Rationale: Huntington disease is an autosomal dominant disorder caused by CAG trinucleotide repeat
expansion in the HTT gene. With one affected parent, each offspring has a 50% probability of inheriting
the mutated allele. The disease exhibits complete penetrance, meaning all individuals with the mutation
will eventually manifest symptoms, typically with anticipation (earlier onset in successive generations
due to repeat expansion).
Q6: A biopsy reveals cells with markedly enlarged, hyperchromatic nuclei and a high nuclear-to-
cytoplasmic ratio, but the tissue architecture remains organized. Which cellular process is most likely
occurring?
A. Anaplasia
B. Dysplasia [CORRECT]
C. Metaplasia
D. Hyperplasia
Correct Answer: B
Rationale: Dysplasia is characterized by disordered cellular development with nuclear pleomorphism,
hyperchromatism, and increased nuclear-to-cytoplasmic ratio, while maintaining some tissue
architectural organization. It represents a pre-neoplastic change that may be reversible if the inciting
stimulus is removed. Unlike anaplasia (complete loss of differentiation seen in malignant tumors),
dysplasia retains recognizable tissue structure.
Q7: A patient with chronic gastroesophageal reflux develops Barrett esophagus. Which cellular
adaptation explains the replacement of squamous epithelium with columnar epithelium?
A. Hypertrophy of existing squamous cells
B. Metaplasia [CORRECT]
C. Hyperplasia of basal squamous cells
D. Apoptosis of damaged surface cells
Correct Answer: B
Rationale: Metaplasia is the reversible replacement of one differentiated cell type with another better
suited to withstand an adverse environment. In Barrett esophagus, chronic acid exposure causes
, squamous epithelium to convert to intestinal-type columnar epithelium, which is more acid-resistant.
While adaptive, this change increases risk for dysplasia and adenocarcinoma if the irritant persists.
Q8: A tumor biopsy shows increased expression of the RAS oncogene with constitutively active GTP-
bound signaling. Which molecular mechanism best explains the pathophysiology?
A. Loss of both alleles of a tumor suppressor gene
B. Gain-of-function mutation converting a proto-oncogene to an oncogene [CORRECT]
C. Defective DNA mismatch repair causing microsatellite instability
D. Epigenetic silencing of a cell cycle inhibitor gene
Correct Answer: B
Rationale: The RAS gene family encodes GTPases that transduce growth factor signals. In normal cells,
RAS cycles between active GTP-bound and inactive GDP-bound states. Oncogenic mutations (typically at
codons 12, 13, or 61) lock RAS in the constitutively active GTP-bound state, leading to continuous
downstream signaling through the MAPK/ERK pathway and uncontrolled cellular proliferation. This
represents a gain-of-function mechanism requiring only one mutated allele.
Section 2: Fluid, Electrolyte & Acid-Base Balance (Q9–Q14)
Q9: A patient with severe vomiting develops metabolic alkalosis. Which compensatory mechanism will
the body employ to correct the acid-base disturbance?
A. Hyperventilation to decrease PaCO₂
B. Hypoventilation to increase PaCO₂ *CORRECT+
C. Increased renal bicarbonate excretion
D. Increased renal hydrogen ion excretion
Correct Answer: B
Rationale: In metabolic alkalosis, the primary compensatory mechanism is hypoventilation, which
increases PaCO₂ and adds respiratory acid to partially offset the excess bicarbonate. The respiratory
system responds within minutes to hours, whereas renal compensation (bicarbonate excretion) requires
2–3 days to become fully effective. Hypoventilation is the immediate compensatory response.
Q10: A patient with chronic heart failure is prescribed loop diuretics and develops muscle weakness,
cardiac arrhythmias, and flattened T waves on ECG. Which electrolyte imbalance and underlying
pathophysiologic mechanism best explain these findings?
A. Hyperkalemia due to decreased renal potassium excretion
