Transcription Flashcards

Transcription Overview

• Transcription is the initial step in gene expression, where DNA sequences are copied into RNA.
• It is crucial for converting genetic information into proteins.

Initiation of Transcription

• RNA polymerase attaches to a specific promoter sequence, which indicates the start of a gene.
• This binding can occur directly or via helper proteins that assist the polymerase.

Template Strand

• One of the DNA strands serves as a template for synthesizing a complementary RNA molecule.
• RNA polymerase specifically uses this template strand during transcription.

Role of RNA Polymerases

• RNA polymerases are enzymes responsible for transcribing DNA into RNA.
• They synthesize RNA using base pairing rules; for example, a G in DNA corresponds to C in RNA.

Structure of RNA and DNA Strands

• DNA and RNA strands possess directionality, marked as 5' and 3' ends.
• The 5' end features a phosphate group, while the 3' end has a hydroxyl group from the sugar ring, essential for transcription directionality.

Function of the Promoter

• The promoter is a specific DNA region where RNA polymerase binds to begin transcription.
• Each gene has a unique promoter that includes sequences for polymerase attachment.

Eukaryotic Promoter Characteristics

• Eukaryotes (like humans) have a complex promoter structure, requiring basal transcription factors to bind before RNA polymerase can attach.
• A common feature in eukaryotic promoters is the TATA box, which aids the binding of transcription factors and interacts with RNA polymerase.

Transcription Elongation

• Following the initiation stage, transcription elongation occurs, during which the RNA strand lengthens as nucleotides are added.
• RNA polymerase moves along the template strand in a 3' to 5' direction, incorporating complementary nucleotides into the growing RNA molecule.