Question

Which of these is the 1^st event to take place during transcription initiation?

(a) Formation of a closed initiation complex

(b) Formation of open initiation complex

(c) Formation of absorptive transcript

(d) Promoter clearance

The question was posed to me during an internship interview.

My doubt stems from Transcription in Prokaryotes : Initiation topic in chapter Gene Expression : Transcription Prokaryotes of Cytogenetics

Answer 1

The correct answer is (b) Formation of open initiation complex

The explanation: When the RNA pol is attached to DNA strands that have still not melted the complex so formed is called open initiation complex. When the DNA melts it is known as open initiation complex. This follows the formation of abortive transcript and promoter clearance.