NBME CBSE MEDICAL EXAMINATION
PREP 2026/2027 QUESTIONS AND
ANSWERS
1. A 4-year-old boy presents with intellectual disability, a musty body odor, and fair skin. A
deficiency in which of the following enzymes is most likely responsible for his condition?
A. Phenylalanine hydroxylase
B. Homogentisate oxidase
C. Tyrosinase
D. Branched-chain alpha-keto acid dehydrogenase
Answer: A
Conceptual Explanation: Phenylketonuria (PKU) is caused by a deficiency in
phenylalanine hydroxylase, leading to accumulation of phenylalanine and a characteristic
musty odor.
2. A 62-year-old man treated with gentamicin for a gram-negative infection develops
decreased urine output and elevated serum creatinine. What is the most likely mechanism of
this drug’s renal toxicity?
A. Immune complex deposition
,B. Glomerular basement membrane thickening
C. Retroperitoneal fibrosis
D. Direct tubular necrosis
Answer: D
Conceptual Explanation: Aminoglycosides like gentamicin cause acute tubular necrosis
(ATN) by direct toxic effects on the proximal tubular cells.
3. A patient with a history of chronic gastroesophageal reflux disease (GERD) undergoes
endoscopy. Biopsy of the lower esophagus shows columnar epithelium with goblet cells. This
represents:
A. Dysplasia
B. Metaplasia
C. Hyperplasia
D. Anaplasia
Answer: B
Conceptual Explanation: Barrett’s esophagus is a classic example of intestinal metaplasia,
where stratified squamous epithelium changes to simple columnar epithelium.
, 4. A 25-year-old male with a history of recurrent pulmonary infections and infertility is
diagnosed with Cystic Fibrosis. Which of the following is the most common genetic mutation
associated with this condition?
A. CAG repeat expansion
B. Nonsense mutation in the dystrophin gene
C. Point mutation in the beta-globin gene
D. Deletion of Phenylalanine at position 508
Answer: D
Conceptual Explanation: The delta-F508 mutation (deletion of phenylalanine) is the most
common mutation in the CFTR gene leading to misfolding and degradation of the protein.
5. Which of the following medications inhibits Vitamin K epoxide reductase, thereby
interfering with the gamma-carboxylation of clotting factors II, VII, IX, and X?
A. Heparin
B. Apixaban
C. Warfarin
D. Clopidogrel
Answer: C
Conceptual Explanation: Warfarin inhibits the enzyme Vitamin K epoxide reductase,
preventing the recycling of Vitamin K required for clotting factor synthesis.
PREP 2026/2027 QUESTIONS AND
ANSWERS
1. A 4-year-old boy presents with intellectual disability, a musty body odor, and fair skin. A
deficiency in which of the following enzymes is most likely responsible for his condition?
A. Phenylalanine hydroxylase
B. Homogentisate oxidase
C. Tyrosinase
D. Branched-chain alpha-keto acid dehydrogenase
Answer: A
Conceptual Explanation: Phenylketonuria (PKU) is caused by a deficiency in
phenylalanine hydroxylase, leading to accumulation of phenylalanine and a characteristic
musty odor.
2. A 62-year-old man treated with gentamicin for a gram-negative infection develops
decreased urine output and elevated serum creatinine. What is the most likely mechanism of
this drug’s renal toxicity?
A. Immune complex deposition
,B. Glomerular basement membrane thickening
C. Retroperitoneal fibrosis
D. Direct tubular necrosis
Answer: D
Conceptual Explanation: Aminoglycosides like gentamicin cause acute tubular necrosis
(ATN) by direct toxic effects on the proximal tubular cells.
3. A patient with a history of chronic gastroesophageal reflux disease (GERD) undergoes
endoscopy. Biopsy of the lower esophagus shows columnar epithelium with goblet cells. This
represents:
A. Dysplasia
B. Metaplasia
C. Hyperplasia
D. Anaplasia
Answer: B
Conceptual Explanation: Barrett’s esophagus is a classic example of intestinal metaplasia,
where stratified squamous epithelium changes to simple columnar epithelium.
, 4. A 25-year-old male with a history of recurrent pulmonary infections and infertility is
diagnosed with Cystic Fibrosis. Which of the following is the most common genetic mutation
associated with this condition?
A. CAG repeat expansion
B. Nonsense mutation in the dystrophin gene
C. Point mutation in the beta-globin gene
D. Deletion of Phenylalanine at position 508
Answer: D
Conceptual Explanation: The delta-F508 mutation (deletion of phenylalanine) is the most
common mutation in the CFTR gene leading to misfolding and degradation of the protein.
5. Which of the following medications inhibits Vitamin K epoxide reductase, thereby
interfering with the gamma-carboxylation of clotting factors II, VII, IX, and X?
A. Heparin
B. Apixaban
C. Warfarin
D. Clopidogrel
Answer: C
Conceptual Explanation: Warfarin inhibits the enzyme Vitamin K epoxide reductase,
preventing the recycling of Vitamin K required for clotting factor synthesis.
