Question

Sigma factors are necessary in which phase of transcription?

1) Activation
2) Elongation
3) Initiation
4) Termination

Answer 1

Sigma factors are necessary for the initiation phase of transcription, where they help RNA polymerase bind to the promoter region to start mRNA synthesis.

Step-by-step explanation:

Sigma factors are essential during the initiation phase of bacterial transcription. They play a key role in the recognition of promoter regions on DNA, which are specific sequences that signal the start of a gene. The sigma factor enables RNA polymerase to bind to these promoter regions, which in case of bacteria include the -10 and -35 sequences. Once bound, the DNA unwinds to allow transcription to commence. After initiation, the sigma factor is released, allowing RNA polymerase to proceed with the elongation of the mRNA strand.