The influenza virus contains an RNA genome. Why do scientists typically have to make a new vaccine for the flu every year?
A. because our bodies develop resistance to the vaccine and it becomes less effective
B. because the virus develops resistance to the vaccine
C. because the virus can mutate into new strains
D. because people change their habits each year and become susceptible to different strains of the virus
E. because the common influenza virus can come from many species of animals including cats and dogs
C. Because the virus can mutate into new strains.
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All of the following are cytokines except
A) interleukins. B) interferons. C) tumor necrosis factor. D) collectins.
About twelve to twenty-four hours after the
previous meal, a person's blood-sugar level normally varies from 60 to 90 milligrams per 100 milliliters of blood, though it may rise to 130 mg/100 ml after meals high in carbohydrates. That the blood-sugar level is maintained within a fairly narrow range despite uneven intake of sugar is due to the body's ability to carry out a. adaptation. b. inheritance. c. metabolism. d. homeostasis. e. all of these processes.
Plant cells ________
A) do not need chloroplasts because their mitochondria meet their energy needs B) have chloroplasts and mitochondria C) use carbon dioxide but do not use oxygen D) do not need mitochondria because their chloroplasts meet their energy needs
The number of molecules with which an enzyme reacts is the
A. end product. B. optimum. C. substrate. D. turnover number.