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10.E: Transcription: RNA polymerases (Exercises)

10.1     What is the role of the sigma factor in transcription, and how does it accomplish this?

10.2     Specific binding of E. coliRNA polymerase to a promoter.  Which of the following statements are correct?

  1. Completely envelopes the DNA duplex (both sides).
  2. requires sigma factor to be part of the holoenzyme.
  3. is enhanced by methylation of purine bases.
  4. results in a temperature-dependent unwinding of about 10 base pairs.

10.3     (POB)  RNA polymerase.  How long would it take for the E. coliRNA polymerase to synthesize the primary transcript for E. colirRNAs (6500 bases), given that the rate of RNA chain growth is 50 nucleotides per second?

10.4     What is the maximum rate of initiation at a promoter, assuming that the diameter of RNA polymerase is about 204 Angstroms and the rate of RNA chain growth is 50 nucleotides per second?

10.5     Although three different eukaryotic RNA polymerases are used to transcribe nuclear genes, the enzymes and their promoters show several features in common.  Are the following statements about common features of the polymerases and their mechanisms of initiation true or false?

  1. All three purified polymerases need additional transcription factors for accurate initiation at promoter sequences.
  2. All three polymerases catalyze the addition of a nucleotide "cap" to the 5' end of the RNA.
  3. For all three polymerases, the TATA‑binding protein is a subunit of a transcription factor required for initiation (not necessarily the same factor for each polymerase).
  4. All three polymerases are composed of multiple subunits.

10.6 What is common and what is distinctive to the reactions catalyzed by DNA polymerase, RNA polymerase, reverse transcriptase, and telomerase?