NBME 27 EDU OBJ EXAM WITH 200 QUESTIONS AND
ANSWERS
1
Exam Section 1: Item 1 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
1. A 40-year-old woman at 5 months' gestation comes to the physician for amniocentesis. Results show
a normal 46,XY karyotype of the fetus. Four months later, the newborn is delivered and
examination shows a female phenotype with mild clitoral enlargement. Ultrasonography shows the
presence of male but not female genital ducts. This newborn most likely has a mutation of
the gene of which of the following factors?
A) Anti-paramesonephric (müllerian) hormone
B) 5a-Reductase
C) SRY protein
D) Steroid sulfatase
E) Zinc finger transcription factor Wilms tumor 1
Correct Answer: B.
5a-Reductase is an enzyme that catalyzes the metabolism of testosterone to dihydrotestosterone (DHT).
Testosterone promotes the development of the mesonephric (wolffian) duct that develops
into the seminal vesicles, epididymis, vas defe - -Objective: 5a-Reductase catalyzes the metabolism of
testosterone to DHT. Individuals with 5a-reductase deficiency exhibit decreased concentrations of DHT
and impaired virilization
of the male urogenital tract. Individuals with 5a-reductase deficiency appear phenotypically female
externally or may have ambiguous external genitalia, with normal male internal genitalia.
II
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-10
Exam Section 1: Item 10 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
10. A 28-year-old man comes to the physician for a routine health maintenance examination. He is from
Jamaica. He has practiced Rastafarianism all his life and follows a diet consisting only
of natural juices, fruits, and grains. He also regularly smokes marijuana as part of his religion. Physical
examination shows no abnormalities. His hematocrit is 32%, and serum vitamin B12
(cobalamin) concentration is within the reference range. Which of the following best describes the
erythrocytes in this patient?
Color
Size (in Diameter)
Shape
,A)
Normal
small
normal
B)
Normal
small
10% sickle, 90% normal
C)
Normal
large
normal
D)
Normal
large
10% sickle, 90% normal
E)
Pale
small
normal
F)
Pale
small
10% sickle, 90% normal
G)
Pale
large
normal
H)
Pale
large
10% sickle, 90% normal
Correct Answer: E.
Choice E correspo - -Objective: Patients who follow a strict vegetarian diet are at risk for iron deficiency
anemia from inadequate dietary heme ingestion. IDA presents with hypochromic, microcytic
erythrocytes on peripheral smear.
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-100
Exam Section 3: Item 1 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
,1. A previously healthy 32-year-old woman comes to the physician because of a 3-month history of
heavy menstrual bleeding, intermittent nosebleeds,
and blood in her urine and stools. She says, "I've had to stop flossing because my gums bleed for an hour
afterwards." Physical examination shows
numerous ecchymoses and petechiae over the lower extremities. A test result for circulating antiplatelet
antibodies is positive. A photomicrograph of
a biopsy specimen of bone marrow is shown. Which of the following is the most likely pathogenesis of
this patient's disease?
A) Inability of the platelets to be released into the blood
B) Megakaryocyte dysfunction
C) Monosomy 7
D) Platelet destruction
O E) Platelet dysfunction
Correct Answer: D.
Platelet destruction as a result of circulating antiplatelet antibodies acc - -Objective: ITP is a diagnosis of
exclusion and presents with mucocutaneous bleeding and severe thrombocytopenia, often following an
upper respiratory illness. It is a result of the
antibody-mediated destruction of circulating platelets, and bone marrow biopsy will demonstrate
increased numbers of megakaryocytes.
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-101
Exam Section 3: Item 2 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
2. In a historical study, 4753 nulliparous women with confirmed pregnancies were randomized to either
folic acid supplementation or trace element supplementation. In both the folic acid and
trace element groups, 88% of the women had pregnancies ending in live birth, late fetal death, stillbirth,
or termination of pregnancy after prenatal diagnosis of a defect. The following
pregnancy outcomes were found:
Drug
Neural tube defects
Folic Acid
0%
1.3%
Trace Elements
0.29%
2.3%
All congenital anomalies
Based on these data, using the trace element group as a control group, which of the following best
represents how many nulliparous women with confirmed pregnancies would have to be
treated with folic acid to prevent one congenital abnormality?
, A) 0
B) 0.29
C) 1.3
D) 2.3
E) 80
F) 100
G) 120
H) 344
1) 4756
Correct - -Objective: The number needed to treat is the number of individuals who need to receive an
intervention in order to prevent one negative outcome. The number needed to treat is the
inverse of the absolute risk reduction.
I3D
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-102
Exam Section 3: Item 3 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
3. A 13-year-old girl is brought to the physician by her mother because of a 5-month history of
behavioral problems. The mother states that her daughter alternates from being sad and socially
withdrawn to being extremely angry and aggressive. After further evaluation, a diagnosis of bipolar
disorder is made. Treatment with valproic acid, which inhibits histone deacetylase, is
started. This drug is most likely to affect which of the following processes in this patient?
A) MRNA splicing
B) Polyadenylation
C) Post-translational processing
D) Transcription
E) Translation
Correct Answer: D.
Valproate, a mood stabilizer used in bipolar disorder, increases DNA transcription by inhibiting histone
deacetylase. Histones are basic proteins with many positively charged amino acid residues,
which attract negatively ch - -Objective: Valproate, a mood stabilizer used in bipolar disorder, increases
transcription by inhibiting histone deacetylase. Acetylation is an epigenetic change that increases DNA
accessibility for transcription.
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ANSWERS
1
Exam Section 1: Item 1 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
1. A 40-year-old woman at 5 months' gestation comes to the physician for amniocentesis. Results show
a normal 46,XY karyotype of the fetus. Four months later, the newborn is delivered and
examination shows a female phenotype with mild clitoral enlargement. Ultrasonography shows the
presence of male but not female genital ducts. This newborn most likely has a mutation of
the gene of which of the following factors?
A) Anti-paramesonephric (müllerian) hormone
B) 5a-Reductase
C) SRY protein
D) Steroid sulfatase
E) Zinc finger transcription factor Wilms tumor 1
Correct Answer: B.
5a-Reductase is an enzyme that catalyzes the metabolism of testosterone to dihydrotestosterone (DHT).
Testosterone promotes the development of the mesonephric (wolffian) duct that develops
into the seminal vesicles, epididymis, vas defe - -Objective: 5a-Reductase catalyzes the metabolism of
testosterone to DHT. Individuals with 5a-reductase deficiency exhibit decreased concentrations of DHT
and impaired virilization
of the male urogenital tract. Individuals with 5a-reductase deficiency appear phenotypically female
externally or may have ambiguous external genitalia, with normal male internal genitalia.
II
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-10
Exam Section 1: Item 10 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
10. A 28-year-old man comes to the physician for a routine health maintenance examination. He is from
Jamaica. He has practiced Rastafarianism all his life and follows a diet consisting only
of natural juices, fruits, and grains. He also regularly smokes marijuana as part of his religion. Physical
examination shows no abnormalities. His hematocrit is 32%, and serum vitamin B12
(cobalamin) concentration is within the reference range. Which of the following best describes the
erythrocytes in this patient?
Color
Size (in Diameter)
Shape
,A)
Normal
small
normal
B)
Normal
small
10% sickle, 90% normal
C)
Normal
large
normal
D)
Normal
large
10% sickle, 90% normal
E)
Pale
small
normal
F)
Pale
small
10% sickle, 90% normal
G)
Pale
large
normal
H)
Pale
large
10% sickle, 90% normal
Correct Answer: E.
Choice E correspo - -Objective: Patients who follow a strict vegetarian diet are at risk for iron deficiency
anemia from inadequate dietary heme ingestion. IDA presents with hypochromic, microcytic
erythrocytes on peripheral smear.
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-100
Exam Section 3: Item 1 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
,1. A previously healthy 32-year-old woman comes to the physician because of a 3-month history of
heavy menstrual bleeding, intermittent nosebleeds,
and blood in her urine and stools. She says, "I've had to stop flossing because my gums bleed for an hour
afterwards." Physical examination shows
numerous ecchymoses and petechiae over the lower extremities. A test result for circulating antiplatelet
antibodies is positive. A photomicrograph of
a biopsy specimen of bone marrow is shown. Which of the following is the most likely pathogenesis of
this patient's disease?
A) Inability of the platelets to be released into the blood
B) Megakaryocyte dysfunction
C) Monosomy 7
D) Platelet destruction
O E) Platelet dysfunction
Correct Answer: D.
Platelet destruction as a result of circulating antiplatelet antibodies acc - -Objective: ITP is a diagnosis of
exclusion and presents with mucocutaneous bleeding and severe thrombocytopenia, often following an
upper respiratory illness. It is a result of the
antibody-mediated destruction of circulating platelets, and bone marrow biopsy will demonstrate
increased numbers of megakaryocytes.
Previous
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-101
Exam Section 3: Item 2 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
2. In a historical study, 4753 nulliparous women with confirmed pregnancies were randomized to either
folic acid supplementation or trace element supplementation. In both the folic acid and
trace element groups, 88% of the women had pregnancies ending in live birth, late fetal death, stillbirth,
or termination of pregnancy after prenatal diagnosis of a defect. The following
pregnancy outcomes were found:
Drug
Neural tube defects
Folic Acid
0%
1.3%
Trace Elements
0.29%
2.3%
All congenital anomalies
Based on these data, using the trace element group as a control group, which of the following best
represents how many nulliparous women with confirmed pregnancies would have to be
treated with folic acid to prevent one congenital abnormality?
, A) 0
B) 0.29
C) 1.3
D) 2.3
E) 80
F) 100
G) 120
H) 344
1) 4756
Correct - -Objective: The number needed to treat is the number of individuals who need to receive an
intervention in order to prevent one negative outcome. The number needed to treat is the
inverse of the absolute risk reduction.
I3D
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-102
Exam Section 3: Item 3 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
3. A 13-year-old girl is brought to the physician by her mother because of a 5-month history of
behavioral problems. The mother states that her daughter alternates from being sad and socially
withdrawn to being extremely angry and aggressive. After further evaluation, a diagnosis of bipolar
disorder is made. Treatment with valproic acid, which inhibits histone deacetylase, is
started. This drug is most likely to affect which of the following processes in this patient?
A) MRNA splicing
B) Polyadenylation
C) Post-translational processing
D) Transcription
E) Translation
Correct Answer: D.
Valproate, a mood stabilizer used in bipolar disorder, increases DNA transcription by inhibiting histone
deacetylase. Histones are basic proteins with many positively charged amino acid residues,
which attract negatively ch - -Objective: Valproate, a mood stabilizer used in bipolar disorder, increases
transcription by inhibiting histone deacetylase. Acetylation is an epigenetic change that increases DNA
accessibility for transcription.
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