Some viruses cause disease; they act as __________
in humans. Fill in the blank(s) with the appropriate word(s).
Answer: pathogens
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Viruses defy characterization as living organisms even though they possess nucleic acids and proteins. The reason why viruses are not considered to be alive is because they
A. form spontaneously. B. cannot form spontaneously. C. cannot reproduce without a host cell. D. lack genetic material.
Evidence of crossing over can often be seen under the light microscope as a structure called a _______.
A. kinetochore B. centromere C. chiasma D. centriole
A common second messenger molecule is
a. a steroid compound. b. cyclic AMP. c. ADP. d. prostaglandin. e. intermedin.
Which of the following is not a source of energy for muscle contraction?
a. creatine phosphate b. glucose c. oxygen d. glycogen e. ATP