Lab 12 | Lac Operon

Operon

A single regulatory region controlling the transcription of multiple genes that are involved in the same process

Gene

All of the regulatory regions & open reading frames

Open Reading Frame (ORF)

A continuous stretch of DNA or RNA that starts with a start codon and ends with a stop codon

Polycistronic mRNA

Multiple open reading frames (prokaryotes)

Monocistronic mRNA

A single open reading frame (eukaryotes)

CAP Binding Protein

Helps CAP protein bind

Lac Repressor

Blocks RNA polymerase in the absence of lactose

CAP

Holds RNA polymerase to transcription regions — is an indirect sensor of lactose & glucose — is an activator

P-EIIA^glu

When phosphorylated, allows adenyl cyclase to resume activity

Adenyl Cyclase

Converts ATP to cAMP

cAMP

Binds to CAP to help it bind to the CAP binding site

β-Galactosidase

Converts lactose to glucose + galactose

Lac permease

Makes the membrane permeable to lactose

Transacetylcyclase

Might remove byproducts of metabolism

ONPG

A colorimetric substrate that turns yellow when β-Galactosidase is active

Absorbance vs Optical Density

Absorbance is a measure of how much light is absorbed by a substance, while optical density (OD) is a measure of total light attenuation (loss)