16-Gene Regulation

1. prokaryotic gene regulation -DRAW, SEQ, HD lac operon -SEQ, CC, HD negative & positive regulation 2. eukaryotic gene regulation -SEQ, CC, HD regulation

what are constitutive genes

housekeeping genes that are expressed continuously by the cell

what are regulated genes?

genes that are expressed only under certain conditions

lac operon

the operon that controls the metabolism of lactose

where is E. coli found?

large intestine

lac operon components

promoter, operator, 3 structural genes

what is the promoter in the lac operon?

binding site for RNA polymerase

what is the operator in the lac operon?

where repressor binds; "on and off switch"

what are the 3 structural genes in the lac operon?

lacZ, lacY, lacA

what is a repressor

a regulatory protein that binds to specific sites on DNA and blocks transcription

negative regulation

repressor binds to the operator and prevents transcription when lactose is absent

when lactose is absent the repressor is active and the operon is ______

off

when lactose is present, but the repressor is inactive, the operon is ______

on

when lactose is present but the repressor is inactive, is there a lot or little mRNA made?

a lot

What is allolactose?

an isomer of lactose that induces lac genes by inactivating repressor

positive regulation

cAMP-CAP trans-acting complex binds to CAP-binding site, causing RNA Pol to more efficiently initiate transcription at the promoter site

If lactose and glucose are present

cAMP levels low, cap inactive, little transcription

if lactose present, and

cAMP levels high, cap is active, lots of transcription

if no lactose and lots of glucose

low cAMP levels, Cap activation low, very little transcription

For smooth, easy binding process you will need more

lactose and no glucose

differential gene

expression of different genes by cells with the same genome leading to cell specialization and different tissue types