George Beadle and Edward Tatum used auxotrophs to determine their "one gene–one enzyme" hypothesis. An auxotroph is best described as:
A. a defective enzyme.
B. a result of nondisjunction.
C. a mutant unable to grow on minimal media.
D. a wild-type version of a model organism.
E. an organism with a dominant lethal mutation.
C
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Some microbes convert iron to magnetite which is then used as an internal compass to help position the microbe correctly in its environment.
Answer the following statement true (T) or false (F)
Body defenses that respond to generalized tissue damage and many common pathogens are referred to as
A) phagocytic. B) antipathogenic responses. C) nonspecific mechanisms. D) lymphomas. E) specific mechanisms.
At the center of an herbaceous eudicot stem is:
a. pith. b. collenchyma. c. sclerenchyma. d. vascular cambium. e. phloem.
In an experiment to track the movement of growth factor molecules from secretion to the point of receptor binding in a particular species of mammal, a student found a 20-fold reduction in mm traveled when in the presence of an adrenal hormone. This is in part attributable to which of the following?
A) The growth factor is a paracrine signal. B) The growth factor depends on osmosis. C) The mammal only carries growth factor through the lymph. D) The growth factor is an exocrine signal. E) The growth factor is an endocrine signal.