Question

The factor responsible for initiations of transcription in bacteria is

• A. Alpha (α)
• B. Beta (β)
• C. Rho (ρ)
• D. Sigma (σ)

Answer 1

The correct option is D

Sigma (σ)

A sigma factor is a protein needed only for initiation of RNA synthesis in bacteria. Sigma factors provide promoter recognition specificity to the RNA polymerase (RNAP) and contribute to DNA strand separation; they then dissociate from RNA polymerase core enzyme following transcription initiation. The mechanism is RNA polymerase core associates with the sigma factor to form RNA polymerase holoenzyme. Sigma factor reduces the affinity of RNA polymerase for nonspecific DNA while increasing specificity for promoters, allowing transcription to initiate at correct sites