At What Point Does the Sigma (σ) Subunit of RNA

Question

At what point does the sigma (σ) subunit of RNA polymerase released from the core enzyme?
A) Prior to the incorporation of any nucleotides into an RNA strand.
B) After transcription begins and about 10 nucleotides have been added to the RNA chain.
C) Just prior to chain termination.
D) Never; it is an intrinsic part of the core enzyme.
E) After RNA polymerase discovers an inverted repeat

Accepted Answer

The sigma subunit is released from the core enzyme after transcription begins and about 10 nucleotides have been added to the RNA chain. This is because the sigma subunit is responsible for recognizing and binding to the promoter region of DNA, and once transcription begins, it is no longer needed for this function.