Tahapan Transkripsi RNA pada Prokariotik

In the previous video, we explored the central dogma of molecular biology, which explains how genetic information is transferred from one molecule to another. The video also mentioned the main differences in genetic expression between prokaryotic and eukaryotic cells. In this video, we will delve into the process of transcription in prokaryotic cells, which involves three major phases: initiation, elongation, and termination, during which mRNA synthesis occurs. Before detailing these phases, the video introduces the enzyme involved in prokaryotic transcription, called RNA polymerase, which consists of several subunits. The Sigma factor facilitates the enzyme's attachment to the DNA, ensuring it binds at the correct position known as the promoter.

The promoter is a DNA region where transcription begins, recognized by the Sigma factor in RNA polymerase. Unlike DNA replication where both strands act as templates (leading to leading and lagging strands), transcription uses only one DNA strand as a template. The template strand facilitates transcription proceeding from upstream (near the 3’ end) to downstream (near the 5’ end). Scientist identify key conserved sequences in promoters, like the -10 or Pribnow box and the -35 region, crucial for transcription initiation, as they aid in recognizing promoter regions and in the initial melting of DNA strands.

During transcription initiation, RNA polymerase attaches to the promoter, unwinds the DNA, and synthesizes a new RNA strand by forming phosphodiester bonds between nucleotides. Transcription occurs from the 5’ to 3’ end, similar to DNA replication, but with only one DNA strand serving as the template. Unlike DNA replication where the replication bubble enlarges, during transcription, the transcription bubble remains the same size but moves with RNA polymerase, which also unwinds DNA upstream and rewinds it downstream, synthesizing an elongated mRNA strand.