Prokaryotic Gene Control

Prokaryotes regulate gene expression primarily

• in order to maintain homeostasis

• in response to changing environmental conditions

• during development as cells specialize

• Prokaryotes do not regulate gene expression. All genes are always on.

An operon is

• a genetic on/off switch in prokaryotes

• a genetic on/off switch in eukaryotes

• a group of related genes and the associated gene switches in prokaryotes

• a group of related genes and the associated gene switches in eukaryotes

Genes can be shut off (not expressed) when a ___ binds to the ____.

• activator, operator

• repressor, operator

• corepressor, operator

• repressor, promotor

What molecule can remove a repressor protein from the operator?

• a corepressor

• an inducer

What is the inducer in the lac operon?

• cAMP

• glucose

• lactose

• CRP

Genes can be turned on (expressed) when a(n) ____ such as CRP or cAMP receptor protein binds to the CRP binding site.

• repressor

• corepressor

• inducer

• activator

In the lac operon system, __ must first bind to CRP so that it is capable of binding to the DNA. This occurs when glucose levels are __.

• cAMP, high

• cAMP, low

• inducer, high

• inducer, low

Negative control of gene expression is mediated by __ and results in a(n) __ in the frequency of transcription.

• activators, increase

• activators, decrease

• repressors, increase

• repressors, decrease

In the trp operon, __ acts as a __ and helps the repressor bind to the operator.

• tryptophan, corepressor

• tryptophan, inducer

• lactose, corepressor

• lactose, inducer

The trp operon has only ___ control which is common for the genes needed for ___ processes.

• positive, catabolic

• positive, anabolic

• negative, catabolic

• negative, anabolic