Cancer is usually due to:
A. exposure to chemicals or radiation.
B. mutations in stem cells.
C. a series of mutations that occur throughout
an affected tissue or organ.
D. a series of mutations that occur in a single
lineage of somatic cells.
E. a series of mutations that occur in multiple
lineages of germ cells.
D
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Two groups of your colleagues are arguing over the amount of energy required for a beaker full of Substance X to complete an endergonic reaction. The first group insists that only the activation energy for a single reaction is necessary, which will release at least enough energy to start a second and third reaction, until all the reactants are consumed. The second group strongly disagrees, insisting that the energy required is equal to the activation energy of a single set of reactants, multiplied by the number of reactant sets in that volume of Substance X. Which group is correct?
a. Group 1 is correct, if and only if the energy released by each set of reactants is sufficient to activate a secondary reaction, after accounting for entropy. b. Group 2 is correct; the amount of energy required must equal the activation energy of all of the reactants in the beaker of Substance X. c. Group 2 is half right; endergonic reactions absorb energy, so free energy, activation energy, and entropy losses for all reactants must be included. d. Neither group is correct; endergonic reactions occur spontaneously, and the reaction has likely been completed unnoticed during this argument.
If water is abundant, a plant's guard cells will and the stomata will .
A. collapse; open B. collapse; close C. swell; close D. None of the answer choices is correct. E. swell; open
Members of the genus Staphylococcus are normally associated with ________.
A. mucous membranes B. skin glands C. skin D. All of the choices are correct.
The hormone oxytocin stimulates ____
a. meiosis of oogonia b. ovulation c. implantation of the embryo d. development of the fetal heart e. contraction of uterine muscles during childbirth