The species extinctions taking place today are
being caused by ____ activities.
a. human
b. volcanic
c. plate tectonic
d. extraterrestrial
e. geothermal
A
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A plant stem would be considered to be
a. a shoot system. b. a tissue. c. a root system. d. a meristem. e. an organ.
The brain knows how strong a stimulus is because the brain interprets ____
a. the neurotransmitter levels the stimulus is producing b. variations in the frequency of action potentials c. the size variation in the action potential being propagated d. the number of ion channels in the plasma membrane of the sensory neuron e. the extent to which voltage gated ion channels open and close
Which statement is NOT correct about the trp operon?
A. Tryptophan acts as the corepressor. B. The structural genes make products that are part of an anabolic pathway for the synthesis of tryptophan. C. Tryptophan binds to the repressor protein and inactivates it. D. It is normally turned off if tryptophan is present.
Where does the bond form that binds one strand of DNA to its other strand?
A) Between the sugar and the base B) Between the phosphate group and the sugar C) Between the bases D) Between the phosphate groups