A sharp reduction in the incidence of Haemophilus influenzae serotype b infections is principally due to
A. the elimination of the natural reservoir of H. influenzae.
B. the development of an effective vaccine.
C. improvements in sanitary conditions in meat processing plants.
D. the discovery of new antibiotics.
Answer: B
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According to the table and the figure above, which enzyme is defective in the strain with the arg2 mutation?
A) the enzyme that converts the precursor to ornithine B) the enzyme that converts ornithine to citrulline C) the enzyme that converts citrulline to arginine D) the enzyme that converts the precursor to citrulline
How did Bayliss and Starling demonstrate that the small intestine secretes chemical signals that stimulate the pancreas to respond to acid?
A. They injected acid into a dog's small intestine after dissecting away all the nerves. B. They exposed a dog's small intestine to a cell extract made from a second dog's small intestine that had been exposed to acid. C. They cut out a piece of the small intestine and exposed it to acid. D. They injected pancreatic secretions from a dog previously exposed to acid into the small intestine of a second dog. E. They injected acid into the pancreas after removing all of its innervation.
C12H24O12; this formula represents a
A. lipid. B. protein. C. carbohydrate. D. phospholipid.
This is another class of intermediate filaments found in epithelial cells:
A. keratin B. myosin C. tubulin D. amino acids E. actin