Question

Describe the process of transcription in prokaryotes/bacterium.

Answer 1

Transcription is the process in which mRNA is produced from the genetic material, which is later translated to produce proteins. Bacterial transcription and translation occur simultaneously in the cytoplasm. Transcription in bacterium/prokaryotes is carried out by RNA polymerase and includes several transcription factors. It is divided into 3 basic steps, initiation, elongation and termination.

1. Initiation: During this step, the DNA is unwound and becomes single-stranded near the initiation site. The RNA polymerase binds to promoter sequence like Pribnow box and starts the transcription of the single-stranded DNA. The binding of RNA polymerase to promoter is facilitates and specified by sigma factor.

2. Elongation: After the synthesis of RNA more than 10 bp long, the sigma factor is removed. The enzyme then moves in 5’- 3’ direction continuously synthesizing RNA.

3. Termination: There are 2 termination mechanisms, namely

i) Rho-independent transcription termination: This involves terminator palindromic sequences within the RNA that signal the RNA polymerase to stop. This sequence forms a hairpin structure. This results in dissociation of RNA polymerase from the DNA template.

ii) Rho-dependent termination: This involves termination factor, rho factor to stop transcription at specific sites. This factor causes dissociation of RNA polymerase from the DNA.