Which statement best describes the role of the E. coli RNA polymerase sigma factor?
a. Sigma factor allows assembly of RNA polymerase.
b. Sigma factor is responsible for catalyzing the formation of phosphodiester bonds during RNA polymerization.
c. Sigma factor shuttles cytoplasmic RNA polymerase to promoter sequences.
d. Sigma factor increases the affinity of RNA polymerase for promoter sequences.
e. Sigma factor actively removes core enzyme from DNA and attaches it to a promoter.
Ans: d
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Punctuated equilibrium is:
a. a theory about the pace of evolutionary change in which rapid periods of evolutionary change are punctuated by longer periods with little change. b. a theory about the pace of evolutionary change in which long periods of evolutionary change are punctuated by short periods with rapid change. c. a way of explaining the idea of "evolution by creeps." d. a way of explaining the idea of "evolution by jerks." e. Both the first and fourth choices are correct.
If you tagged organic carbon inside a chloroplast with a fluorescent label, the location most likely to have a high concentration of labeled carbon would be in the
A. between the outer and inner membranes. B. stroma. C. inside the thylakoid. D. thylakoid membrane.
Which of the following statements concerning plasma cells is FALSE?
A) They live for many years and function as memory cells. B) They are descended from activated B cells. C) They can produce large quantities of antibodies on a daily basis. D) They secrete a single type of antibody molecule specific for a single epitope. E) The antibodies they produce can remain in circulation for weeks.
Which of the following are magnifying lenses?
A) objectives B) oculars C) condensers D) prisms E) both objectives and the oculars