In trees, such as the horse chestnut, the abscission of leaves and fruits in the fall is mediated by ____.
A. abscisic acid
B. auxin
C. ethylene
D. cytokinin
E. gibberellin
Answer: C
You might also like to view...
A set of SNPs close together on a chromosome is called a(n) ____________________. Fill in the blank(s) with the appropriate word(s)
A symptom of a transmissible spongiform encephalopathy (TSE) is:
a. degeneration of the digestive tract. b. progressive immune deficiency. c. degeneration of the brain and central nervous system. d. inflammation of the reproductive organs. e. influenza-like symptoms
Although the reactions of the Calvin cycle do not depend directly on light, they do not usually occur at night. Why?
A) It is usually too cold at night for these reactions to take place. B) Carbon dioxide concentrations decrease at night. C) The Calvin cycle depends on products of the light reactions that cannot occur at night. D) Plants must open their stomata to restore their water balance each night. E) At night, plants have a negative water balance with the soil, due to reduced evaporation
You are interested in cell-size regulation and discover that signaling through an enzyme-coupled receptor is important for the growth (enlargement) of mouse liver cells
Activation of the receptor activates adenylyl cyclase, which ultimately leads to the activation of PKA, which then phosphorylates a transcription factor called TFS on threonine 42. This phosphorylation is necessary for the binding of TFS to its specific sites on DNA, where it then activates the transcription of Sze2, a gene that encodes a protein important for liver cell growth. You find that liver cells lacking the receptor are 15% smaller than normal cells, whereas cells that express a constitutively activated version of PKA are 15% larger than normal liver cells. Given these results, predict whether you would expect the cell's size to be bigger or smaller than normal cells if cells were treated in the following fashion. A. You change threonine 42 on TFS to an alanine residue. B. You create a version of the receptor that is constitutively active. C. You add a drug that inhibits adenylyl cyclase. D. You add a drug that increases the activity of cyclic AMP phosphodiesterase. E. You mutate the cAMP-binding sites in the regulatory subunits of PKA, so that the complex binds cAMP more tightly.