Gene Expression In Prok

Question 0

How do operon a work?

Answer 0

They have a single promoter with which multiple genes can be transcribed with as one transcript encoding multiple proteins.
They have operator near promoter

Question 1

Describe the genomic organization of prokaryotes

Answer 1

DNA is not tightly packed, not broken up into extrons and introns. Genes that function together are physically close and are regulated together- operon.

Question 2

What does a repressor do?

Answer 2

When it is bound to the promoter it the gene is no longer transcribed. Usually prevents RNAP from binding or prevents it from. Moving to 3’ to transcribe.

Question 3

How do operon a respond to regulation?

Answer 3

Positive- the default is off so amd environmental cue must bind to the activator to recruit RNAP to the promoter. Or an inducer which binds to the repressor and prevents it from working.
Negitive- the default is on so needs an environmental cue to allow it to bind to the operator and prevent transcription

Question 4

Describe the tryptophan operon.

Answer 4

Encodes 5 enzymes that make tryptophan from scratch. Neg regulation is used to turn off when appropriate. Co repressors cause conformational change so repressor binds to the operator, stopping RNAP from transcribing.

Question 5

Describe the lactose operon.

Answer 5

Encodes 2 genes that allow prok to use lactose. Used when lactose is available. Default is off so repressor binds operator. Lactose serves as inducer amd alters the shape amd repressor fails to bind.
Also. Reds co activators to indicate when glucose is low.