Which of the following characteristics of transcription initiation by ?70-containing polymerase holoenzymes is different than for ?54-containing polymerase holoenzymes?
A. The holoenzyme binds to its promoter to initially form a closed complex.
B. The formation of the closed complex is readily reversible.
C. The closed complex spontaneously converts to the open complex.
D. The opening of the DNA duplex is accompanied by energetically favorable conformational changes in the holoenzyme.
E. Initiation is primer-independent.
C
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The drug RU486, or Mifepristone, functions by _____
A) inhibiting release of gonadotropins from the pituitary B) blocking progesterone receptors in the uterus C) preventing release of the secondary oocyte from the ovary D) reducing sexual interest E) prolonging the endurance of the corpus luteum
Which one of the following cellular components is NOT directly involved in synthesis or secretion of
molecules in the cell?
a. ribosomes b. lysosome c. rough endoplasmic reticulum d. Golgi complex e. smooth endoplasmic reticulum
Which of the following choices is not a mechanism by which enzymes generally speed reactions?
a. orienting substrates in favorable positions b. helping substrates get together c. permanently donating a proton or electron to the reaction d. inducing a fit between enzyme and substrate
In a hypotonic solution, a plant cell will ________
A) undergo plasmolysis B) become flaccid C) burst D) become turgid