Killed or inactivated vaccines are prepared by
A. treatment with formalin, heat, or radiation.
B. removal of virulence genes from the microbe.
C. passage of the pathogen through unnatural hosts or tissue culture.
D. long-term subculturing of the microbe.
E. All of these choices are correct.
Answer: A
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Is the regulation of blood sugar levels in the body a negative feedback loop or a positive feedback loop?
A. negative feedback loop B. positive feedback loop
Which of the following statements is NOT important to Darwin's theory of natural selection?
a) all species have the ability to produce more offspring than can live and reproduce b) variation is found in all natural populations c) offspring tend to inherit characteristics acquired by their parents during their lifetimes d) some variation found in natural populations is heritable e) none of the above choices is correct; all are important to his theory
Earthworms possess both male and female organs on separate segments. Mating could be described as "parallel parking" in opposite directions, and cross-fertilizing. Given this information, which of the following is (are) true?
A. Maintaining any system not clearly male or female is disadvantageous; the earthworm is trapped in an evolutionary dead end. B. This is primarily to allow them to self-fertilize if no other worm is in their sector of the soil. C. This is evidence of a primitive state that is generally less efficient than separate sexes. D. This is an advantage since they can mate with any other earthworm of the same species that they encounter.
The surgeon who advocated using disinfectants on hands and in the air prior to surgery was
A. Louis Pasteur. B. Joseph Lister. C. Antonie van Leeuwenhoek. D. Robert Koch. E. Ignaz Semmelweis.