Operons

define operon

a group of genes that operate together

what do operons do?

regulate gene expression in prokaryotes

structural genes

genes that code for proteins

regulatory gene

codes for repressor protein

trp operon

repressible operon

lac operon

group of genes involved in lactose metabolism

inducer

A specific small molecule that inactivates the repressor in an operon.

What is a co-repressor?

A molecule that binds to the repressor.

What does a co-repressor do to the repressor?

It causes the repressor to be active.

What is the effect of an active repressor on transcription?

It inhibits transcription.

What does an active repressor bind to?

The operator.

When arabinose is present in the environment…

repressor is inactive

RNA polymerase can access promoter

the genes are expressed

when arabinose is absent in the environment…

repressor is active

RNA cannot access the promoter

genes will not be transcribed