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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 • • • • • • 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 • • • • 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 • • • • 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