GENE REGULATIONThe turning on and off of genes

Allows organisms to respond to environmental changes

Ex: lac Operon in bacteria

E coli

E. COLI AND LACTOSE E. coli uses 3 enzymes to metabolize

lactose. 2 control sequences are located next

to the lactase enzymesPromoter – site where RNA

polymerase attaches and initiates transcription

Operator – acts as a switch (determining whether RNA polymerase can attach to promoter and start transcription)

OPERON

A cluster of genes with related functions, promoter, and an a operator

Occurs in prokaryotes

REPRESSORProtein that functions by binding to the operator

Blocks the attachment of RNA polymerase to the promoter region

Molecule that turns off transcription

Cells have a regulatory gene to make the repressor

ACTIVATORSProteins that turn operons on by binding to DNA

Makes it easier for the RNA polymerase to bind to the promoter

Allows bacteria to survive in frequently changing environments.

EUKARYOTES AND GENE EXPRESSION

Each eukaryote gene has its own promoter and other control sequences

The default state for most genes tend to be “off”

11-08-TurningOnAGeneAnim.mov