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• A 6-year-old male with vision problems and mental
retardation dies of a massive stroke. Autopsy reveals
middle cerebral artery thrombosis and old renal
infarcts. Which of the following supplements could
have prevented this patient’s death?
• A. tyrosine
• B. thiamine
• C. ascorbic acid
• D. pyridoxine
• E. methionine
• F. vitamin K
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A concerned parent brings their
adolescent child for a routine
checkup to rule out a genetic
hemoglobinopathy. The patient has a
sister and brother with the said
hemoglobinopathy that causes them
to be anemic. A hemoglobin
electrophoresis is performed that is
depicted in the figure below. The
adolescent is determined to have the
trait of the disease. sample is run
with controls including normal, sickle
cell trait and sickle cell anemia and
serum. Which one of the lanes
contains the adolescent’s sample?
Lane A
Lane B
Lane C
Lane D
Lane E
• AN INFANT BORN TO A 23-YEAR-OLD FEMALE DEVELOPS
VOMITING AND LETHARGY SEVERAL DAYS AFTER BIRTH.
PHYSICAL EXAMINATION REVEALS HYPERTONicity and
muscle rigidity. The mother also notices an odor of burnt
sugar in her diapers. Which of the following amino acids
should most likely be restricted in this infant’s diet?
• A. tyrosine
• B. phenylalanine
• C. methionine
• D. lysine
• E. leucine
• F. histidine
• A group of investigators is studying the effect
of various factors on the shape of the oxygendissociation curve for hemoglobin. The shift
from the red curve to the blue curve in the
graph below would most likely be caused by
which of the following?
• A. strenuous exercise
• B. adaptation to high
altitude
• C. hypoventilation
• D. chronic anemia
• E. severe hypothermia
• A 44-year-old homeless male develops
confusion and ophthalmoplegia. Upon review
of the medical record, you discover that he
has been admitted to the hospital with alcohol
intoxication several times before. Which of the
following reactions is most likely impaired in
this patient?
• A diagram illustrating
the DNA replication
process is shown below.
Which of the points
marked by letters
represents the site of
action of helicase in the
following diagram?
• A mutation in the TATA box of a eukaryotic gene
that codes for a transmembrane protein is most
likely to affect which of the following functions?
• A. DNA methylation
• B. translation initiation
• C. RNA elongation
• D. posttranscriptional RNA splicing
• E. transcription initiation
• A mutation that leaves prokaryotes unable to
replicate their DNA is induced in an experimental
setting. The ability to remove RNA primers during
DNA replication is affected by this experimental
mutation. Which of the following enzymes is most
likely nonfunctional?
• A. helicase
• B. Primase
• C. DNA polymerase III
• D. DNA polymerase I
• E. gyrase
• F. ligase
• Some proteins that participate in bacterial DNA
synthesis have specific exonuclease activity. Which of
the following is the best statement about the 3’ to 5’
exonuclease activity of DNA polymerase III?
• A. IT REMOVES AN IMPROPER BASE-PAIR
NUCLOETIDE DURING REPLICATION
• B. IT CUTS dna AT SPECIFIC dna SEQUENCES
• C. IT NICKS THE dna strands that have formed
thymidine dimers
• D. it cleaves DNA strands to relax positive supercoils
• E. it can remove groups of nucleotides (up to ten) at
a time a
• An agent applied to human cells is believed to
activate G-protein dependent phospholipase
C. Which of the following intracellular
substances is most likely to increase
immediately after exposure to this agent?
• A.Ca2+
• B. Camp
• C. CI
• D. NO
• E. Mrna
• F. cGMP
• Dna exonuclease hydrolytically remove one
nucleotide at a time from the end of a DNA
chain. Which of the following enzymes has 5’
to 3’ exonuclease activity?
• A. helicase
• B. gyrase
• C. primase
• D. DNA polymerase I
• E. DNA polymerase III
• F. ligase
• A 38-year-old male is being evaluated for a long history
of pain and stiffness in both shoulders and both knees.
Physical examination shows brown spots on his sclerae
and diffuse darkening of the helix of his ears. Which of
the following enzymes is most likely deficient in this
patient?
• A. tyrosinase
• B. dopamine hydroxylase
• C. phenylallanine hydroxylase
• D. homogentisic acid oxidase
• E. branched –chain ketoacid dehydrogenase
• Some human cells are unable to generate NADPH
from glucose metabolism but are able to
synthesize ribose from fructose-6-phosphate.
Which of the following enzymes is essential for
the latter finding?
• A. enolase
• B. aconitase
• C. transketolase
• D. glutathione reductase
• E. glucose-6-phosphate dehydrogenase
• A 12-year-old male is evaluated for ataxia accompanied by
episodic erythematous and pruritic skin lesions and loose
stools. Laboratory evaluation reveals loss of neutral
aromatic amino acids in the urine. This patient’s symptoms
would most likely respond to which of the following
supplements?
• A. niacin
• B. Folic acid
• C. riboflavin
• D. niacin
• E. pyridoxine
• F. ascorbate
• Activity of an enzyme called aldose reductase in
the lens of a healthy indiviidual produces sorbitol
that can not exit the cells. Which of the following
is the most likely product of sorbitol oxidation in
these cells?
• A. glucose
• B. Fructose
• C. galactose
• D. galactitol
• E. xylulose
• The DNA replication process ineukaryotic cells closely
mimics that in prokaryotic cells, but the volume of
genetic material to be replicated is typically much
greater in eukaryotic cells. Which of the following
ensures fast DNA replication in eukaryotic cells?
• A. energy-independent DNA unwinding
• B. No RNA primers synthesized during replication
• C. multile origins of replication
• D. continuous synthesis of the lagging strand
• E. no proofreading by DNA polymerase
• A 5-year-old girl is brought to the physician by her mother.
The mother tells you that the girl’s skin is becoming red and
scaling with only minimal sun exposure. She began to nitice
this pahenomenon when the child was 7 months old. Now
the girl’s skin is thin and hyperpigmented. The patient has
few nevi on her hands that have been rapidly enlarging. The
defective gene in this patient is responsible for:
• A. regulation of cell cycle
• B. signal transduction
• C. DNA mismatch repair
• D. DNA excision repair
• E. regulation of apoptosis
• A 32-year-old male with Down syndrome experiences
significant cognitive decline, making him totally
dependent on a caregiver for his basic daily activities.
Cortical neurons in this patient are most likely to
demonstarte which of the following?
• A. pick bodies
• B. Lewy bodies
• C. neurofibrillary tangles
• D. negri bodies
• E. psammoma bodies
• F. spongiform transformation
• A 42-year-old woman comes to the neurologist for enrollment in a
research study. She has a 15-year history of resting tremor,
bradykinesia and cogwheel rigidity consistent with Parkinson’s
disease. One of her siblings recently started having similar
symptoms. Genetic analysis is performed on the patient and her
affected sibling. The result shows a loss-of-function mutation in a
gene that leads to an accumulation of misfolded proteins. Which of
the following biochemical processes is most likely defective in this
patient?
•
• Acetylation
• Gamma-carboxylation
• Glucuronidation
• Phosphorylation
• Ubiquitination
• A 2-day-old infant born to a 22-year-old female
demonstrates a good appetite despite some weight
loss. Physical examination is within normal limits.
Which of the following hemoglobin compositions most
likely dominates in this patient?
• α₂β₂
• α₂γ₂
• α₂δ₂
• ξ₂ε₂
• γ₄
• A patient is suspected of having an inherited disorder.
Pedigree analysis shows te following pattern below
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• This patient is most likely to be suffering from which of
the following conditions?
• A. Hemophilia A
• B. Huntington’s disease
• C. Osteogenesis imperfect
• D.Ehlers Danlos syndrome
• A patient is suspected of having
an inherited disorder. Pedigree
analysis shows the following
pattern below
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• This patient is most likely to be
suffering from which of the
following conditions?
• A. Hemophilia A
• B. Huntington’s disease
• C.Osteogenesis imperfect
• D.Ehlers Danlos syndrome
• E. None of the above
• A 13-month-old girl has a history of recurrent bacterial
infections. Production of O₂⁻, H₂O₂ and .OH by
neutrophils is normal and production of HOCI is
decreased following stimulation by opsonized bacteria.
The most likely cause is deficiency of
• Catalase
• Glutathione peroxidase
• Myeloperoxidase
• NADPH oxidase
• Superoxide dismutase
• A healthy 30-year-old man is participating in a study o the effects of
a competitive inhibitor of endothelial nitric oxide synthase. After
intravenous injection o the inhibitor, blood pressure immediately
increases. Supplementation with which of the following amino acids
is most appropriate to reverse this increase?
• Arginine
• Aspartic acid
• Glutamic acid
• Leucine
• Lysine
• Methionine
• Tyrosine
• The ability of endothelial cells to inhibit platelet
aggregation is mediated in part by the
metabolism of cell membrane-derived
arachidonic acid by which of the following?
• Anaerobic glycolysis
• Cyclooxygenase pathway
• Glutathione reductase pathway
• Mixed function oxidase pathway
• Lysosomal enzymes pathway
• Tricarboxylc acid pathway
• a 2-yer-old boy has a unilateral cleft lip and cleft palate. He
has no other malformations and is otherwise healthy. He
has no family history of birth defects. His parents are not
related. Which of the following genetic mechanisms is most
likely to have caused these congenital abnormalities?
• Autosomal dominant inheritance
• Autosomal recessive inheritance
• Chromosome deletion
• Chromosomal aneuploidy
• Mitochondrial inheritance
• X-linked recessive inheritance
• Several tissues uses triglyceride breakdown
products as intermediates in energy generation
and glucose synthesis. Which of the following is a
liver-specific enzyme that facilitates such
reactions?
• Acyl CoA synthetase
• Glycerol kinase
• Glucose-6-phosphate dehydrogenase
• Acetyl CoA carboxylase
• ATP-citrate lyase
• Urea is an essential molecule generated by the
body for the disposal of nitrogen. Which of the
following is an immediate source of nitrogen for
urea in the urea cycle?
• Glutamine
• N-acetylgutamate
• Asparagine
• Aspartate
• Alanine
• A female infant born to a 29-year-old woman following
an uncomplicated vaginal delivery is found to have
swelling of the hands and posterior neck mass. The
mass is composed of cystic spaces separated by
connective tissue rich in lymphoid aggregates. The
infant most likely suffers from
• Cri du chat syndrome
• Down’s syndrome
• Turner’s syndrome
• Sandhoff disease
• Sly disease
• A neonate born to 41-year-old woman in her 39th week
of gestation has a flattened face and epicanthal folds.
The child’s echocardiography reveals an endocardial
cushion defect. Which of the following most likely
occurred prior to conception?
• Meiotic non-disjunction
• Robertsonian translocation
• Expansion of trinucleotide repeats
• Formation of fragile site
• Inactivation of one chromosome
• Deletion of chromosome part.
• A nuclear enzyme transfers a methyl group from
S-adenosyl-methionine to a cytosine residue in a
DNA molecule. This enzyme is implicated in
which of the following processes?
• Aneuploidy
• Anticipation
• Imprinting
• Meiotic nondisjunction
• pleiotropy