For a repressible operon to be transcribed, which of the following must occur?
A) A corepressor must be present.
B) RNA polymerase and the active repressor must be present.
C) RNA polymerase must bind to the promoter, and the repressor must be inactive.
D) RNA polymerase must not occupy the promoter, and the repressor must be inactive.
C
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In viruses, genetic information flows from ________ to ________
A) RNA / virion B) nucleic acid / protein C) capsid / virion D) DNA / protein
What is one reason that invasive species such as the brown tree snake in Guam are often so successful in their new habitat?
A. They are better adapted to winter conditions. B. They are unable to full partition existing resources. C. Potential prey animals have evolved defenses against it. D. The species has no natural predators to control it. E. Such a species is typically a Batesian mimic.
The most critical step in the Gram stain is the application of the:
a. safranin. b. crystal violet. c. Gram's iodine. d. Gram's decolorizer.
Since the 1970s, approximately 40 new infectious disease agents have been discovered, including SARS, chikungunya and zika. The ability of these agents to spread rapidly and cause global concern is due to all of the following except
A. communities are spreading into rural areas/wildlife habitats. B. individuals are traveling more frequently and farther distances than in the previous half-century. C. communities are becoming more sparsely populated. D. communities are becoming more densely populated.