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Biochemistry
1. Foreign antigen recognition at the cell surface by cytotoxic T-lymphocytes stimulates a response that results in rapid cell death. Which of the following act as effectors of this response?
A. Matrix metalloproteinases
B. Acid hydrolases
C. Caspases
D. Phospholipase A2
E. Protein kinase A
2. A 5-day-old boy is diagnosed with hyperphenylalaninemia by newborn screening. He is placed on a special phenylalanine-restricted diet with tyrosine supplementation. The parents are extensively counseled on the patient’s condition and informed of the necessary dietary restrictions. They are also instructed to return to the clinic for regular follow-up visits. Several months later, laboratory results indicate that the infant has a normal serum phenylalanine level. Careful examination, however, shows some neurologic abnormalities, including axial hypotonia. Further work-up is notable for elevated prolactin. Impaired synthesis of a cofactor essential for metabolism of aromatic amino acids is suspected. Which of the following enzymes is most likely deficient in this patient?
A. Dihydropteridine reductase
B. Dopamine beta-hydroxylase
C. PhenylaJanine hydroxylase
D. Phenylethanolamine N-methyltransferase
E. Tyrosinase
3. A 54-year-old man comes to the emergency department with a 3-month history of fatigue and exertional dyspnea. He has early satiety and frequent upper abdominal discomfort. On physical examination, the patient has palpable splenomegaly but no lymphadenopathy. Laboratory tests are as follows:
Reverse transcription polymerase chain reaction is used to diagnose chronic myelogenous leukemia in this patient. Which of the following is most likely to be detected by this test?
A. Chromosomal position of the BCR and ABL genes
B. DNA rearrangement in the BCR promoter region
C. Fusion protein containing BCR and ABL domains
D. Messenger RNA transcript containing BCR and ABL exons
E. Point mutation in the ABL enhancer region