All of the following are true of hypersensitivity EXCEPT
A) it occurs in the presence of an antigen.
B) it is synonymous with "allergy."
C) it occurs when an individual is exposed to an allergen for the first time.
D) it is due to an altered immune response.
E) it requires previous exposure to an antigen.
C
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Which one of the following statements about DNA is incorrect?
A. DNA typically exists in cells as a double helix. B. There are 10 base pairs per turn in a helical DNA molecule. C. DNA has a diameter of approximately 2 nanometers. D. The strands in DNA wrap around each other in a helix that coils to the right. E. All of the statements about DNA are correct.
How is the rho protein triggered in rho-dependent termination of prokaryotic transcription?
a. Rho protein encounters a region rich in C-G nucleotides and a stable hairpin forms. b. Rho protein is triggered by the ?’ subunit of polymerase. c. A run of G nucleotides will stall polymerase and rho protein collides with it from behind. d. Upstream nucleotides in a pattern of TATAAT triggers the rho protein to bring polymerase to a halt.
d. The neurotransmitter opens ion channels in the dendrite’s plasma membrane.
a. The plasma membrane is depolarized, resulting in a decrease in the voltage across the neuron membrane. b. Sodium ions enter the neuron. c. An electrical signal is received by the dendrite, and it then travels passively to the neuron body. d. The neurotransmitter opens ion channels in the dendrite’s plasma membrane.
B cells are genetically programmed to produce unique antibodies; similarly, T cells are genetically programmed to
produce unique T-cell receptors. a. True b. False