gene expression

Operon

A single on/off switch that controls multiple related genes at once.

Promoter

The DNA part where RNA polymerase binds to start transcription.

Operator

The switch that determines whether RNA polymerase can move forward.

Structural genes

The genes that code for enzymes or proteins.

Repressor protein

A protein that blocks transcription during negative regulation.

Activator

A molecule that allows transcription during positive regulation.

trp Operon

A repressible operon that makes tryptophan, which stops synthesis when tryptophan is present.

lac Operon

An inducible operon that breaks down lactose and is activated when lactose is present.

Corepressor

A substance that binds to a repressor protein, enabling it to block transcription.

Inducer

A substance that inactivates a repressor, allowing transcription to occur.

Prokaryotes

Organisms that possess operons and regulate gene expression at transcription only.

Eukaryotes

Organisms that do not have operons and regulate gene expression at multiple levels including transcription and RNA processing.

Catabolic pathways

Metabolic pathways that break down molecules for energy.

Anabolic pathways

Metabolic pathways that build complex molecules from simpler ones.

Enhancers

DNA sequences that increase transcription when bound by activators.

Silencers

DNA sequences that decrease transcription when bound by repressors.

Alternative splicing

A process that allows different proteins to be produced from the same gene by removing certain non-coding regions.

Post-translational modification

The process by which proteins are modified after translation to become active.