Chapter 16 - Regulation of gene expression in prokayotes

Positive Control

Increasing frequency of initiation; Activator proteins enhance binding of RNA polymerase

Negative Control

Decrease the frequency of transcription; repressor proteins bind to operators in DNA and block transcription; also includes the removing of a repressor

Major groove and Minor groove

Major groove is more accessible

A Operon

Prokaryotic cells; a series of genes that code for enzymes that are all part of a single metabolic pathway are where the expression is simultaneously controlled; Includes the operator and promoter

Inducible Operon

Usually OFF; Inducer turns it on by deactivating the repressor; usually catabolic;

Repressible operon

Usually ON;The repressor blocks gene expression by blocking RNA polymerase, and binding to the repressor turns it off; usually anabolic;

Operator

A gene that positioned next to the promoter

Represser

Binds to the operator and blocks RNA polymerase; what causes inducable operators to be off most of the time; A protein

Inducer

Binds to the repressor and prevents it from binding to the operator; causes Repressible operons to be on most of the time; not a protein

Co-repressor

a molecule that works with the represser to switch off a operon

Lac Operon

codes for an enzyme that consumes lactose; usually off but represser cant bind to operator when lactose is present; thus a induceable operon

Trp operon

produces trp; usually ON; turns off when trp is present; thus a repressable operon