Which of the following is a unique characteristic of viruses that distinguishes them from the other major groups of microorganisms?
A. Viruses lack cell structure.
B. Viruses cause human disease.
C. Viruses contain genetic material.
D. Vruses are composed of cells that lack nuclei.
E. Viruses cannot be seen without an electron microscope.
Answer: A
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How many different kinds of base pairings are in DNA?
A) Hundreds or thousands B) Two C) Millions D) Four
An organism is discovered that consumes a considerable amount of sugar, yet does not gain much weight when denied air. Curiously, the consumption of sugar increases as air is removed from the organism's environment, but the organism seems to thrive even in the absence of air. When returned to normal air, the organism does fine. Which of the following best describes the organism?
A) It must use a molecule other than oxygen to accept electrons from the electron transport chain. B) It is a normal eukaryotic organism. C) The organism obviously lacks the citric acid cycle and electron transport chain. D) It is an anaerobic organism. E) It is a facultative anaerobe.
The most likely method by which the mutated CCR5 gene prevents AIDS is by
A) covering the cell membrane. B) rupturing the nuclear membrane. C) attacking and destroying the HIV virus particles. D) coding for a protective protein in the cell membrane.