Question

What is transcription? Briefly describe the mechanism of transcription in prokaryotes.

Hint:

In prokaryotes, transcription = DNA → mRNA. Steps: Initiation, Elongation, Termination. No introns, so RNA does not need splicing.

Answer 1

Definition: Transcription is the process by which the genetic information from DNA is copied into RNA. In prokaryotes, this RNA is usually mRNA, which directly participates in protein synthesis. 

Steps of Transcription in Prokaryotes: \[\begin{array}{rl} 1. & \text{Initiation:} \\ \bullet & \text{RNA polymerase enzyme binds to the promoter region of DNA.} \\ \bullet & \text{The sigma factor helps in recognizing the promoter sequence.} \\ \bullet & \text{DNA strands unwind at the transcription start site.} \\ 2. & \text{Elongation:} \\ \bullet & \text{RNA polymerase moves along the DNA template strand (3' → 5').} \\ \bullet & \text{Complementary RNA nucleotides are added, forming the mRNA strand (5' → 3').} \\ 3. & \text{Termination:} \\ \bullet & \text{Transcription stops when RNA polymerase reaches a terminator sequence.} \\ \bullet & \text{The RNA transcript (mRNA) is released and the enzyme detaches from DNA.} \\ \end{array}\] 

Significance: In prokaryotes, transcription and translation occur simultaneously in the cytoplasm, ensuring quick protein synthesis.