Prokaryotic Transcription: Initiation and Promotor Sequences

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4 Questions

What is the role of the sigma 70 subunit in RNA Polymerase during transcription initiation?

Binds to promotor sequences

How does the efficiency of transcription initiation differ for strong promoters compared to weak promoters?

Strong promoters are transcribed more frequently than weak promoters

Which consensus sequence is recognized by the sigma 70 subunit of E. coli RNA Polymerase's holoenzyme at -10?

TATAAT

What happens to the sigma 70 subunit of RNA Polymerase before elongation begins?

It is released from the core enzyme

Study Notes

Transcription Initiation

  • The sigma 70 subunit of RNA Polymerase plays a crucial role in recognizing specific DNA sequences, known as promoters, to initiate transcription
  • It acts as a specificity factor, binding to the promoter region, and positioning the RNA Polymerase correctly to initiate transcription

Promoter Strength

  • Strong promoters have a higher efficiency of transcription initiation compared to weak promoters
  • This is due to the strength of the interaction between the sigma 70 subunit and the promoter region

Sigma 70 Recognized Consensus Sequence

  • The sigma 70 subunit of E. coli RNA Polymerase's holoenzyme recognizes the consensus sequence -10 element (TATAAT) at the -10 position
  • This consensus sequence is essential for transcription initiation

Sigma 70 before Elongation

  • Before elongation begins, the sigma 70 subunit of RNA Polymerase is released, allowing the core enzyme to continue transcribing the DNA template
  • This release enables the transition from the initiation stage to the elongation stage of transcription

This quiz covers the process of transcription initiation in prokaryotes, focusing on how RNA Polymerase recognizes and binds to promotor sequences. It specifically discusses the consensus sequences -10 (TATAAT) and -35 (TTGACA) recognized by s70 in E.coli's RNA Polymerase holoenzyme.

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