9/26/25, 5:50 PM NBME 30 <span style="color:#000;font-weight:bold;">200+</span> (2025-2026 A+ Graded) Exam-Style Questions | Verified Solutio…
NBME 30 Exam Questions and Answers
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Question 1
1
Exam Section 1: Item 1 of 50
National Board of Medical Examiners®
Comprehensive Basic Science Self-Assessment
1. Shortly after delivery, a full-term male newborn is found to have black hair with a
white forelock. His mother, a brunette, also has a white forelock and wears hearing
aids. Physical examination shows heterochromia of irides. Otoacoustic emissions
testing and
brain stem auditory evoked responses show bilateral sensorineural hearing loss.
Which of the following is the most likely cause of the findings in this patient?
A) Abnormal neural crest development
B) Abnormality of connexins
C) Deficiency of homogentisic acid oxidase activity
D) Deficiency of tyrosinase activity
E) Failure of internalization of melanin granules by keratinocytes
F) Failure of melanosome transportation along dendrites
Correct Answer
A.
Abnormal neural crest development leads to Waardenburg syndrome. Waardenburg
syndrome is a syndrome of patchy depigmentation of the skin, hair, irises, and
cochlear dysfunction that primarily illustrates an autosomal dominant inheritance
pattern. Because of
genetic mutations of genes encoding transcription factors, neural crest cells do not
properly differentiate into melanoblasts (melanocyte precursors), or melanoblasts
do not migrate to their appropriate location. Patients typically have a white forelock
and eyelashes,
depigmented skin patches, iridic heterochromia, and sensorineural deafness. The
eyes may also be laterally displaced. The clinical diagnosis may be confirmed with
genetic testing. Treatment includes audiologic evaluation and genetic consultation.
Incorrect Answers: B, C, D, E, and F.
An abnormality of connexins (Choice B) would lead to abnormal formation of the
plasma membrane channels of diverse cell types. Different combinations of
sensorineural hearing loss, ichthyosis, alopecia, and peripheral neuropathy may
occur. Depigmentation
would be atypical.
Deficiency of homogentisic acid oxidase activity (Choice C) would lead to decreased
metabolism of the amino acids phenylalanine and tyrosine, which instead degrade
into homogentisic acid. Homogentisic acid accumulates in the skin and joints,
causing increased
pigmentation and arthritis, respectively. Depigmentation would be atypical.
Deficiency of tyrosinase activity (Choice D) occurs in oculocutaneous albinism, which
presents with uniformly hypopigmented hair and skin (versus the patchy
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,9/26/25, 5:50 PM NBME 30 <span style="color:#000;font-weight:bold;">200+</span> (2025-2026 A+ Graded) Exam-Style Questions | Verified Solutio…
depigmentation of Waardenburg syndrome) and eye abnormalities (eg, iris
hypopigmentation, refractive
errors, nystagmus). In tyrosinase deficiency, melanocytes are unable to synthesize
melanin from the amino acid tyrosine. Iridic heterochromia and sensorineural
deafnes
Page 3 of 399
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, 9/26/25, 5:50 PM NBME 30 <span style="color:#000;font-weight:bold;">200+</span> (2025-2026 A+ Graded) Exam-Style Questions | Verified Solutio…
Question 2
2
Exam Section 1: Item 2 of 50
National Board of Medical Examiners®
Comprehensive Basic Science Self-Assessment
2. During an experiment, a solution of mixed fatty acids is injected into the duodenum
of an experimental animal. Under these conditions, the clearance rate of an
intravenous glucose load from the circulation is doubled. In contrast, an injection of
an equal
volume amount of 0.9% saline into the duodenum has much less effect on the plasma
clearance rate of glucose. These findings are most likely caused by the secretion of
which of the following hormones?
A) Gastrin
B) Glucose-dependent insulinotropic peptide
C) Motilin
D) Secretin
E) Somatostatin
Correct Answer
B.
Glucose-dependent insulinotropic peptide (GIP) is secreted by K cells in the
duodenum and jejunum and functions to decrease gastric acid production and
stimulate insulin release from the pancreas. Its secretion is promoted by the
presence of fatty acids, amino
acids, and intestinal glucose. While serum glucose also stimulates insulin secretion
by the pancreas, the effect of intraluminal glucose on GIP and subsequent insulin
secretion leads to increased concentrations of insulin compared to parenteral
glucose
administration. Insulin promotes peripheral tissue uptake of glucose, glycolysis,
glycogen synthesis, protein synthesis, and fatty acid synthesis, resulting in
decreased glucose concentration in the serum.
Incorrect Answers: A, C, D, and E.
Gastrin (Choice A) is produced by G cells in the gastric antrum and stimulates
parietal cells within the gastric body to produce hydrochloric acid. Gastric acid has
no effect on serum glucose concentration.
Motilin (Choice C) is secreted by the small intestine and stimulates intestinal
peristalsis. Motilin receptors are targeted by erythromycin and metoclopramide,
used therapeutically in gastroparesis.
Secretin (Choice D) is produced by duodenal S cells. It promotes the release of
bicarbonate-rich pancreatic secretions and bile and inhibits gastric acid production.
Somatostatin (Choice E) is a regulatory peptide secreted by D cells of the pancreas
and gastrointestinal mucosa that inhibits gastric acid and pepsinogen secretion,
gallbladder contraction, and insulin and glucagon release. Somatostatin would have
an indirect
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NBME 30 Exam Questions and Answers
Latest
Page 1 of 399
1/399
,9/26/25, 5:50 PM NBME 30 <span style="color:#000;font-weight:bold;">200+</span> (2025-2026 A+ Graded) Exam-Style Questions | Verified Solutio…
Question 1
1
Exam Section 1: Item 1 of 50
National Board of Medical Examiners®
Comprehensive Basic Science Self-Assessment
1. Shortly after delivery, a full-term male newborn is found to have black hair with a
white forelock. His mother, a brunette, also has a white forelock and wears hearing
aids. Physical examination shows heterochromia of irides. Otoacoustic emissions
testing and
brain stem auditory evoked responses show bilateral sensorineural hearing loss.
Which of the following is the most likely cause of the findings in this patient?
A) Abnormal neural crest development
B) Abnormality of connexins
C) Deficiency of homogentisic acid oxidase activity
D) Deficiency of tyrosinase activity
E) Failure of internalization of melanin granules by keratinocytes
F) Failure of melanosome transportation along dendrites
Correct Answer
A.
Abnormal neural crest development leads to Waardenburg syndrome. Waardenburg
syndrome is a syndrome of patchy depigmentation of the skin, hair, irises, and
cochlear dysfunction that primarily illustrates an autosomal dominant inheritance
pattern. Because of
genetic mutations of genes encoding transcription factors, neural crest cells do not
properly differentiate into melanoblasts (melanocyte precursors), or melanoblasts
do not migrate to their appropriate location. Patients typically have a white forelock
and eyelashes,
depigmented skin patches, iridic heterochromia, and sensorineural deafness. The
eyes may also be laterally displaced. The clinical diagnosis may be confirmed with
genetic testing. Treatment includes audiologic evaluation and genetic consultation.
Incorrect Answers: B, C, D, E, and F.
An abnormality of connexins (Choice B) would lead to abnormal formation of the
plasma membrane channels of diverse cell types. Different combinations of
sensorineural hearing loss, ichthyosis, alopecia, and peripheral neuropathy may
occur. Depigmentation
would be atypical.
Deficiency of homogentisic acid oxidase activity (Choice C) would lead to decreased
metabolism of the amino acids phenylalanine and tyrosine, which instead degrade
into homogentisic acid. Homogentisic acid accumulates in the skin and joints,
causing increased
pigmentation and arthritis, respectively. Depigmentation would be atypical.
Deficiency of tyrosinase activity (Choice D) occurs in oculocutaneous albinism, which
presents with uniformly hypopigmented hair and skin (versus the patchy
Page 2 of 399
2/399
,9/26/25, 5:50 PM NBME 30 <span style="color:#000;font-weight:bold;">200+</span> (2025-2026 A+ Graded) Exam-Style Questions | Verified Solutio…
depigmentation of Waardenburg syndrome) and eye abnormalities (eg, iris
hypopigmentation, refractive
errors, nystagmus). In tyrosinase deficiency, melanocytes are unable to synthesize
melanin from the amino acid tyrosine. Iridic heterochromia and sensorineural
deafnes
Page 3 of 399
3/399
, 9/26/25, 5:50 PM NBME 30 <span style="color:#000;font-weight:bold;">200+</span> (2025-2026 A+ Graded) Exam-Style Questions | Verified Solutio…
Question 2
2
Exam Section 1: Item 2 of 50
National Board of Medical Examiners®
Comprehensive Basic Science Self-Assessment
2. During an experiment, a solution of mixed fatty acids is injected into the duodenum
of an experimental animal. Under these conditions, the clearance rate of an
intravenous glucose load from the circulation is doubled. In contrast, an injection of
an equal
volume amount of 0.9% saline into the duodenum has much less effect on the plasma
clearance rate of glucose. These findings are most likely caused by the secretion of
which of the following hormones?
A) Gastrin
B) Glucose-dependent insulinotropic peptide
C) Motilin
D) Secretin
E) Somatostatin
Correct Answer
B.
Glucose-dependent insulinotropic peptide (GIP) is secreted by K cells in the
duodenum and jejunum and functions to decrease gastric acid production and
stimulate insulin release from the pancreas. Its secretion is promoted by the
presence of fatty acids, amino
acids, and intestinal glucose. While serum glucose also stimulates insulin secretion
by the pancreas, the effect of intraluminal glucose on GIP and subsequent insulin
secretion leads to increased concentrations of insulin compared to parenteral
glucose
administration. Insulin promotes peripheral tissue uptake of glucose, glycolysis,
glycogen synthesis, protein synthesis, and fatty acid synthesis, resulting in
decreased glucose concentration in the serum.
Incorrect Answers: A, C, D, and E.
Gastrin (Choice A) is produced by G cells in the gastric antrum and stimulates
parietal cells within the gastric body to produce hydrochloric acid. Gastric acid has
no effect on serum glucose concentration.
Motilin (Choice C) is secreted by the small intestine and stimulates intestinal
peristalsis. Motilin receptors are targeted by erythromycin and metoclopramide,
used therapeutically in gastroparesis.
Secretin (Choice D) is produced by duodenal S cells. It promotes the release of
bicarbonate-rich pancreatic secretions and bile and inhibits gastric acid production.
Somatostatin (Choice E) is a regulatory peptide secreted by D cells of the pancreas
and gastrointestinal mucosa that inhibits gastric acid and pepsinogen secretion,
gallbladder contraction, and insulin and glucagon release. Somatostatin would have
an indirect
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