Question

An in vitro transcription system that contains a bacterial gene initiates transcription, but from random points on the DNA. Which of the following proteins most likely is missing from the reaction?

a. sigma factor
b. rho factor
c. RNA polymerase II
d. TATA-binding protein

Answer 1

Option (a), The missing protein from the in vitro transcription system initiating transcription at random DNA points is the sigma factor, which is crucial for recognizing the promoter and guiding RNA polymerase to initiate transcription correctly.

Step-by-step explanation:

If an in vitro transcription system containing a bacterial gene initiates transcription from random points on the DNA, the protein most likely missing from the reaction is the sigma factor. In prokaryotic transcription, the sigma factor plays a critical role in recognizing promoter sequences and guiding the RNA polymerase to the correct initiation site for transcription. The sigma factor binds to the -35 sequence in the promoter region, which then allows the RNA polymerase to bind and initiate transcription accurately at the promoter region.

In the absence of the sigma factor, the RNA polymerase can still transcribe RNA, but it would not be able to recognize the promoter efficiently and would start transcription at various random locations along the DNA. This scenario leads to the transcription of random sequences rather than the specific gene of interest. This specific binding of the sigma factor to the promoter is essential to ensure that only the appropriate genes are transcribed.