Question

What is transcription? Explain the process of transcription in prokaryotes/bacteria by a labelled diagram.

Answer 1

Hint: It is the process in both prokaryotes and eukaryotes. This process tends to undergo some stages and results in the formation of a type of RNA.

Complete answer:
Transcription is defined as a process in which the information is copied from a DNA strand to a messenger mRNA. Messenger mRNA results from the enzyme RNA polymerase.
Prokaryotic transcription is also termed as the bacterial transcription where the piece of bacterial DNA is duplicated into a newly synthesized strand of messenger RNA which is later translated to produce proteins with the use of enzyme RNA polymerase and other transcription factors.

Bacterial transcription occurs in the cytoplasm of the cell and the process occurs in three basic steps:
-Initiation: In this step, the double helix DNA strand is distressed and set off single stranded to the initiation site. The RNA polymerase enzyme binds to the promoter sequence (TATA box) and starts the transcription of the single stranded DNA. The sigma factors are responsible for binding of the RNA polymerase enzyme to the promoter.
-Elongation: After the synthesis of more than 8-9 base pairs of lengthy RNA, the sigma factor is eliminated from the promoter. The RNA polymerase enzyme then moves in 5’-3’ direction continuously all the while synthesizing RNA.
-Termination: This is the end stage which halts the process of transcription. It has two types of mechanisms-
Rho independent transcription termination: transcription is terminated due to specific sequence in terminator DNA. The terminator DNA contains invert repeats which causes complementary pairing as transcript RNA from the hairpin structure. The results in the dissociation of RNA polymerase from the DNA template.
Rho dependent transcription termination: transcription is terminated by rho proteins. It gets attached to RNA after the translation completes but transcription still goes on. This factor leads to the removal of RNA polymerase from the DNA.

Note: Bacterial transcription differs from eukaryotic transcription as in bacterial transcription occurs in the cytoplasm of the cell whereas eukaryotic transcription occurs in the nucleus of the cell. Bacterial RNA polymerase is of single type while eukaryotes have three different RNA polymerase enzymes.