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σ factor

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Microbiology

Definition

σ factor is a protein needed for the initiation of transcription in bacteria. It enables RNA polymerase to bind to specific promoter regions on DNA.

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5 Must Know Facts For Your Next Test

  1. σ factor helps RNA polymerase recognize and bind to promoters.
  2. Different σ factors recognize different sets of promoters, allowing for differential gene expression.
  3. The primary σ factor in E. coli is σ70, which recognizes most housekeeping genes' promoters.
  4. Alternative σ factors are used during specific conditions, such as heat shock or nitrogen starvation.
  5. σ factors dissociate from RNA polymerase after the initiation of transcription, allowing elongation to proceed.

Review Questions

  • What role does the σ factor play in bacterial transcription?
  • How do alternative σ factors contribute to gene regulation?
  • Why does the σ factor dissociate from RNA polymerase after transcription initiation?

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