Lecture 3: Expression of the genetic code: Transcription

Central Dogma of Molecular Biology

DNA → RNA → Protein; describes the flow of genetic information in a cell.

Gene

A sequence of DNA that codes for a protein or RNA molecule.

Gene Expression

The process by which information in DNA is used to synthesize proteins (via transcription and translation).

Promoter

A DNA sequence where RNA polymerase binds to initiate transcription.

Terminator

A DNA sequence signaling RNA polymerase to stop transcription.

Exons

Coding regions of a gene that remain in mRNA and are translated into proteins.

Introns

Non-coding sequences that are removed during mRNA processing.

General Transcription Factors

Help RNA polymerase bind to the promoter and initiate transcription.

Regulatory Transcription Factors

Enhance or repress gene transcription by interacting with regulatory DNA sequences.

Activators

Increase transcription by binding to enhancers.

Repressors

Decrease transcription by binding to silencers.

Enhancers

DNA sequences that increase gene expression.

Silencers

DNA sequences that suppress gene expression.

RNA Polymerase

Synthesizes RNA from a DNA template.

RNA Polymerase II

The enzyme that transcribes protein-coding genes in eukaryotes.

5' → 3' Direction

The direction in which RNA polymerase synthesizes RNA.

Template Strand

The DNA strand that RNA polymerase reads to create the RNA transcript.

5’ Cap

A modified guanine nucleotide added to protect mRNA and aid in ribosome binding.

Poly-A Tail

A string of adenines added to the 3’ end of mRNA for stability and transport.

Splicing

The removal of introns and joining of exons in mRNA processing.

Alternative Splicing

The process where different exons are included or excluded, producing multiple proteins from the same gene.

Differential Gene Expression

The process by which different cells express different sets of genes, leading to cell specialization.

Transcription vs. DNA Replication

Transcription makes RNA from DNA; DNA replication makes an entire DNA copy.

Does transcription copy both DNA strands?

No, only the template strand is copied.