The cleavage activity is intrinsic to RNA polymerase itself, it is stimulated greatly by accessory factors that are ubiquitous in the three biological kingdoms. There are two such factors in E. coli, GreA and GreB, and eukaryotic RNA polymerase II uses TFIIS for the same purpose. 

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#Id: 902

#Unit 13. Methods in Biology

Flow cytometry or FACS is the sine qua non (without which, nothing) of the modern immunologist’s toolbox.

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#Id: 3094

#Unit 3. Fundamental Processes

Initiation timing depends on accumulating the active initiator protein DnaA and on inhibitors that turn off newly synthesized origins until the next cell cycle

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#Id: 2125

#Unit 8. Inheritance Biology

G-banding patterns reveal that several human chromosomes differ from those of chimpanzees by only a pericentric inversion.

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#Id: 7355

#Unit 11. Evolution and Behavior

The overall change in allelic frequency is a balance between the opposing forces of forward mutation and reverse  mutation:

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#Id: 9314

#Unit 4. Cell Communication and Cell Signaling

3 or 4 cGMP molecules must bind to each channel in order to open it; because of this cooperative allosteric interaction, channel opening is very sensitive to small changes in cGMP levels.