COMSAE Phase 1 Form 115 Practice Exam
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026|2026Q&A |
Instant Download Pdf
1. A 6-year-old boy presents with recurrent epistaxis. Physical exam
shows telangiectasias on the lips and mucosa. Which inheritance pattern
best explains this condition?
A. X-linked recessive
B. Autosomal recessive
C. Mitochondrial
D. Autosomal dominant
Rationale: Telangiectasias with recurrent nosebleeds suggest hereditary
hemorrhagic telangiectasia, which is inherited in an autosomal dominant
pattern.
2. Which enzyme deficiency causes phenylketonuria (PKU)?
A. Phenylalanine hydroxylase
B. Tyrosine aminotransferase
C. Homogentisate dioxygenase
D. Branched-chain α-ketoacid dehydrogenase
Rationale: Classic PKU results from deficiency of phenylalanine
hydroxylase, preventing conversion of phenylalanine to tyrosine.
,3. A drug that prolongs QT interval most likely blocks which cardiac
channel?
A. Sodium channel (fast)
B. Delayed rectifier potassium channel (I_Kr)
C. L-type calcium channel
D. Funny current (I_f)
Rationale: Blockade of the rapid delayed rectifier K⁺ current (I_Kr)
slows repolarization and prolongs the QT interval.
4. During embryonic development, the neural crest gives rise to all
EXCEPT:
A. Melanocytes
B. Schwann cells
C. Adrenal medulla chromaffin cells
D. Hepatocytes
Rationale: Neural crest cells contribute to melanocytes, peripheral
neurons/Schwann cells, and adrenal medulla; hepatocytes arise from
endoderm.
5. Which of the following bacteria is most commonly associated with
dental caries?
A. Staphylococcus aureus
B. Streptococcus mutans
C. Escherichia coli
D. Pseudomonas aeruginosa
,Rationale: S. mutans metabolizes sugars to acid and initiates enamel
demineralization—key in dental caries.
6. In a patient with primary hyperaldosteronism (Conn syndrome), you
would expect:
A. Hyperkalemia and metabolic acidosis
B. Hypokalemia and metabolic alkalosis
C. Hyponatremia and metabolic acidosis
D. Hyperkalemia and respiratory alkalosis
Rationale: Excess aldosterone causes sodium retention, potassium loss
(hypokalemia), and H⁺ loss leading to metabolic alkalosis.
7. The steep part of the oxyhemoglobin dissociation curve is important
because:
A. It ensures maximal loading at the lungs
B. It facilitates oxygen unloading in tissues with small PO₂ changes
C. It indicates cooperative binding of CO₂
D. It shows that Hb is saturated at low PO₂
Rationale: The steep portion allows tissues to extract more O₂ for a
modest drop in PO₂; reflects cooperative O₂ binding.
8. Which vitamin deficiency causes beriberi?
A. Niacin (B3)
B. Thiamine (B1)
, C. Pyridoxine (B6)
D. Cobalamin (B12)
Rationale: Thiamine deficiency affects pyruvate dehydrogenase and
other enzymes, causing beriberi (wet/dry) and Wernicke
encephalopathy.
9. A 30-year-old man has painless lymphadenopathy and Reed-Sternberg
cells on biopsy. Which diagnosis is most likely?
A. Non-Hodgkin lymphoma
B. Acute lymphoblastic leukemia
C. Hodgkin lymphoma
D. Chronic lymphocytic leukemia
Rationale: Reed-Sternberg cells are characteristic of Hodgkin
lymphoma, often presenting with painless lymph node enlargement.
10. A 24-year-old woman with a family history of breast cancer is found
to have a pathogenic mutation in the BRCA1 gene. Which inheritance
pattern is most consistent with this condition?
A. Autosomal dominant
B. Autosomal recessive
C. X-linked recessive
D. Mitochondrial
Correct answer: A. Autosomal dominant
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026|2026Q&A |
Instant Download Pdf
1. A 6-year-old boy presents with recurrent epistaxis. Physical exam
shows telangiectasias on the lips and mucosa. Which inheritance pattern
best explains this condition?
A. X-linked recessive
B. Autosomal recessive
C. Mitochondrial
D. Autosomal dominant
Rationale: Telangiectasias with recurrent nosebleeds suggest hereditary
hemorrhagic telangiectasia, which is inherited in an autosomal dominant
pattern.
2. Which enzyme deficiency causes phenylketonuria (PKU)?
A. Phenylalanine hydroxylase
B. Tyrosine aminotransferase
C. Homogentisate dioxygenase
D. Branched-chain α-ketoacid dehydrogenase
Rationale: Classic PKU results from deficiency of phenylalanine
hydroxylase, preventing conversion of phenylalanine to tyrosine.
,3. A drug that prolongs QT interval most likely blocks which cardiac
channel?
A. Sodium channel (fast)
B. Delayed rectifier potassium channel (I_Kr)
C. L-type calcium channel
D. Funny current (I_f)
Rationale: Blockade of the rapid delayed rectifier K⁺ current (I_Kr)
slows repolarization and prolongs the QT interval.
4. During embryonic development, the neural crest gives rise to all
EXCEPT:
A. Melanocytes
B. Schwann cells
C. Adrenal medulla chromaffin cells
D. Hepatocytes
Rationale: Neural crest cells contribute to melanocytes, peripheral
neurons/Schwann cells, and adrenal medulla; hepatocytes arise from
endoderm.
5. Which of the following bacteria is most commonly associated with
dental caries?
A. Staphylococcus aureus
B. Streptococcus mutans
C. Escherichia coli
D. Pseudomonas aeruginosa
,Rationale: S. mutans metabolizes sugars to acid and initiates enamel
demineralization—key in dental caries.
6. In a patient with primary hyperaldosteronism (Conn syndrome), you
would expect:
A. Hyperkalemia and metabolic acidosis
B. Hypokalemia and metabolic alkalosis
C. Hyponatremia and metabolic acidosis
D. Hyperkalemia and respiratory alkalosis
Rationale: Excess aldosterone causes sodium retention, potassium loss
(hypokalemia), and H⁺ loss leading to metabolic alkalosis.
7. The steep part of the oxyhemoglobin dissociation curve is important
because:
A. It ensures maximal loading at the lungs
B. It facilitates oxygen unloading in tissues with small PO₂ changes
C. It indicates cooperative binding of CO₂
D. It shows that Hb is saturated at low PO₂
Rationale: The steep portion allows tissues to extract more O₂ for a
modest drop in PO₂; reflects cooperative O₂ binding.
8. Which vitamin deficiency causes beriberi?
A. Niacin (B3)
B. Thiamine (B1)
, C. Pyridoxine (B6)
D. Cobalamin (B12)
Rationale: Thiamine deficiency affects pyruvate dehydrogenase and
other enzymes, causing beriberi (wet/dry) and Wernicke
encephalopathy.
9. A 30-year-old man has painless lymphadenopathy and Reed-Sternberg
cells on biopsy. Which diagnosis is most likely?
A. Non-Hodgkin lymphoma
B. Acute lymphoblastic leukemia
C. Hodgkin lymphoma
D. Chronic lymphocytic leukemia
Rationale: Reed-Sternberg cells are characteristic of Hodgkin
lymphoma, often presenting with painless lymph node enlargement.
10. A 24-year-old woman with a family history of breast cancer is found
to have a pathogenic mutation in the BRCA1 gene. Which inheritance
pattern is most consistent with this condition?
A. Autosomal dominant
B. Autosomal recessive
C. X-linked recessive
D. Mitochondrial
Correct answer: A. Autosomal dominant
