Transcription and RNA Synthesis

Transcription

• A single DNA molecule can contain hundreds or thousands of genes, but only those being expressed are copied into RNA at a given time.
• Transcription is the process of copying a base sequence from DNA to RNA.
• The product of transcription is an RNA molecule, unlike DNA replication which produces a duplicate of DNA.
• In transcription, segments of DNA serve as templates to produce complementary RNA molecules.

The Role of RNA Polymerase

• RNA polymerase is the enzyme responsible for carrying out transcription.
• RNA polymerase binds to DNA and separates the DNA strands.
• It uses one strand of DNA as a template to assemble nucleotides into a complementary strand of RNA.
• The ability to quickly copy a DNA sequence into RNA enables a single gene to produce hundreds or thousands of RNA molecules.

Initiation and Termination of Transcription

• RNA polymerase binds to specific regions of DNA called promoters, which have unique base sequences.
• Promoters are regions of DNA that can bind to RNA polymerase, indicating where to start transcription.
• Other regions of DNA cause transcription to stop when an RNA molecule is completed, indicating where to terminate transcription.