The Steps of Transcription: Initiation, Elongation, and Termination Explained

Steps of Transcription

Transcription is the process by which genetic information stored in DNA is converted into messenger RNA (mRNA) molecules

Transcription is the process by which genetic information stored in DNA is converted into messenger RNA (mRNA) molecules. This process occurs in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells. The steps of transcription include initiation, elongation, and termination. Here is a detailed explanation of each step:

1. Initiation:
– RNA polymerase binding: The first step of transcription is the binding of RNA polymerase to the DNA template. RNA polymerase is an enzyme that catalyzes the synthesis of RNA. It recognizes specific DNA sequences called promoters that indicate the starting point for transcription.
– Open complex formation: Once RNA polymerase binds to the promoter region, the DNA helix unwinds, forming an open complex. This creates a small transcription bubble where the DNA template strand is accessible for RNA synthesis.

2. Elongation:
– RNA synthesis: In this step, RNA polymerase adds ribonucleotides to the growing RNA chain according to the complementary base-pairing rules. RNA polymerase moves along the DNA template strand in a 3′ to 5′ direction, synthesizing the new RNA molecule in a 5′ to 3′ direction.
– DNA rewinding: As RNA polymerase moves forward, it rewinds the DNA helix behind it. This rewinding helps to prevent the formation of secondary DNA structures and maintains the stability of the DNA molecule.

3. Termination:
– Transcription termination signal: At the end of the gene being transcribed, a termination signal is encountered. This signal can be either a specific DNA sequence or a structural element within the RNA molecule. It causes RNA polymerase to detach from the template DNA strand and release the newly synthesized RNA molecule.
– RNA processing (in eukaryotes): In eukaryotes, the newly synthesized primary RNA transcript, also known as pre-mRNA, undergoes additional processing steps before it can be used as a template for protein synthesis. These include capping, polyadenylation, and splicing.

After transcription, the newly synthesized RNA molecule, now called mRNA, undergoes further processing and leaves the nucleus (in eukaryotes) to reach the ribosomes in the cytoplasm, where it serves as a template for protein synthesis during translation.

Overall, transcription is a highly regulated process that ensures the accurate and efficient synthesis of RNA molecules from DNA templates, allowing for the expression of genetic information.

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