Question

You wanted to isolate active RNA polymerase (with a part of the transcript associated with it ) from cellular mix. For this, you perform an immunoprecipitation with anti sigma antibody. Then you check the precipitate. What will you observe?

(a) RNA polymerase with transcript

(b) RNA polymerase without transcript

(c) Only antibody

(d) DNA with associated RNA polymerase and a transcript

I have been asked this question in an interview for job.

Question is taken from Transcription in Prokaryotes : Initiation topic in division Gene Expression : Transcription Prokaryotes of Cytogenetics

Answer 1

The correct answer is (b) RNA polymerase without transcript

Best explanation: Sigma factor dissociates after initiation so anti sigma antibody will only pull down RNA polymerase prior to promoter clearance. Thus, the polymerases so obtained have no transcript associated.