Prokaryotic Gene Regulation

Question 1

what are prokaryotic genes controlled by?

Answer 1

operons

Question 2

what is an operon?

Answer 2

is a stretch of DNA that includes the operator, promoter and the gene they control.

Question 3

define RNA polymerase

Answer 3

is a transcription enzyme.

Question 4

define a promoter

Answer 4

is the site where RNA polymerase binds to.

Question 5

define the operator

Answer 5

is a place where the repressor binds.

Question 6

define the repressor

Answer 6

binds to the operator and restricts RNA polymerase from coding the mRNA.

Question 7

define genes (structural genes)

Answer 7

are what the RNA polymerase reads and creates mRNA molecules from.

Question 8

When is the lac operon used?

Answer 8

lac operon- breaks down lactose- lactose is used when glucose is not present

Question 9

what does the lac operon contain?

Answer 9

promoter, lac gene , and operator

Question 10

What type of reaction is the lac operon and is it repressible or inducible

Answer 10

Inducible: normally off but can be turn on & catabolic reaction

Question 11

what is a regulatory gene/ Lac I gene

Answer 11

lies upstream of the operon & has its own promoter (not part of the operon) & produces the repressor protein→ can toggle between active or inactive shape

Question 12

What happens if there is no lactose- present

Answer 12

active repressors are bound to the operator and block them when no lactose is present

Question 13

What does allolactose do?

Answer 13

binds to repressor & converts the repressor into the inactive form= removing the repressor from the RNA

Question 14

what happened if there are low glucose levels and lactose is present?

Answer 14

Active CAP protein is trying to enhance transcription rate
cAMP binds to inactive CAP= active
→ active cap attaches to promoter & increases affinity of RNA polymerase to bind to the promoter & it enhances transcription rate

Question 15

what happens if there is high glucose levels but lactose is present?

Answer 15

Don’t need lactose because glucose is available; glucose is easier to break down (monosaccharides) & its accessible
cAMP levels are low
Inactive lac repressor
RNA polymerase will still bind but the transcription rate will remain low

Question 16

Where is the trp operon?

Answer 16

on the E.coli genome

Question 17

What happens to the trp operon when tryptophan is abundant?

Answer 17

Tryptophan would bind to repressor so it binds to the operator& it would prevent RNA polymerase from translating the rest of the sequence

Question 18

what happens to the trp operon when tryptophan is not abundant?

Answer 18

The trp repressor is inactive and is away from the operator when tryptophan is NOT in abundance in tWherhe environment.
RNA polymerase will continue coding for the tryptophan synthesis

Question 19

Are trp operons repressible or inducible and are they catabolic/ anabolic?

Answer 19

Repressible operon- can become repressed
Anabolic reaction