Question

(a) Identify strands 'A' and 'B' in the diagram of transcription unit given above and write the basis on which you identified them. 

(b) State the functions of Sigma factor and Rho factor in the transcription process in a bacterium. 

(c) Write the functions of RNA polymerase-I and RNA polymerase-III in eukaryotes.

Answer 1

(a) A-Template strand = 1 

B-Coding strand: 1 

Template strand has polarity 3'-5' 

Coding strand has polarity 5'-3' 

On the basis of polarity with respect to promoter.

(b) In initiation sigma factor associates with RNA polymerase to initiate transcription, Rho factor gets associated to RNA polymerase to terminate transcription.

(c) RNA polymerase I - Transcribes -RNAs 

RNA polymerase III - Transcribes tRNA / 5srRNA / 5nRNA.