Chapter 11: Prokaryotic gene regulation

What did francois jacob, Jacques monod, and Andre Lwoff discover?

The genetic control of enzyme and virus synthesis

How can bacteria utilize lactose?

By hydrolyzing the disaccharide of lactose into 2 monosaccharides, glucose and galactose

What do structural genes in lac operons do?

They encode for proteins to hydrolyze lactose and are only expressed when needed

What is Lac Z?

An enzyme that primarily breaks the covalent bonds in the disaccharide of lactose

What is Lac Y?

A transporter enzyme that sits on the plasma membrane of the cell that brings in lactose to be broken down

What is the operator sequence?

A sequence in an operon found only in bacteria that sits between the promoter region and coding sequence and has the ability to turn on or off all genes associated with a process

How are Lac operons regulated?

They are regulated by the promoter region

How are lac operons expressed in bacteria?

Allolactose binds to the repressor protein and removes it from the operator region, allowing for an mRNA transcript to be produced containing lac genes that produce 3 proteins important for the break down of lactose

How does allolactose remove repressor proteins from the operator region?

By binding to the protein and changing its conformation. causing it to dissociate it from the operator region and allow transcription to occur

how was the lac system discovered?

By determining whether lactose can be metabolized in bacteria and if it can live off it

What occurred in the first experiment relating to the lac system?

Pieces of mutated DNA was introduced into bacterial cells, which caused scientists to realize that there is a region between the promoter region and coding sequence, which lead to the discovery of the operator region

What are Oc mutants?

DNA sequences that contain a mutated operator region that no longer allows for repressor proteins to bind, allowing for lac Z and Y to be expressed regardless of lactose being present or not

What if a DNA copy with a nonfunctional lac Z is introduced to a normal copy with a functional lac Z?

the lac Z is still expressed by both copies

What is the super suppressor mutant?

A mutation of the repressor protein that causes the protein to lose its ability to bind to allolactose, meaning that when it binds to an operator region it can never be removed since it cant recognize allolactose

Whats occurs when a DNA copy with a super suppressor is introduced to a normal copy in the absence of lactose?

The mutant repressor will bind to both operator regions in the copies and prevent transcription from occurring

What occurs if a DNA copy with a super suppressor is introduced to a normal copy when lactose is present?

The mutant repressor will only bind to its operator region and prevent transcription, while the normal copy will be able to transcribe

What is CAP?

A transcription activator that boosts an expression when paired with cAMP and cannot bind to the promoter region without cAMP

What occurs when lactose is present and glucose is low?

cAMP and CAP will bind together and bind to the promoter region, allowing for transcription to occur much quicker and more efficient

What occurs when no lactose is present and glucose is low in a bacteria cell?

The repressor protein will remain in the operator region and prevent cAMP and CAP from binding to the region and begin transcription

What occurs when lactose is present and glucose is high in a bacteria cell?

The repressor protein will become absent and the cAMP and CAP molecules dont bind to the promoter region, causing transcription to occur but at a low level