Chapter 18 - Bacterial Gene Expression

Question 1

Why do bacterial use post-translational gene control?

Answer 1

Because most genes are on all the time.

Question 2

What is lactose composed of?

Answer 2

Glucose and Galactose

Question 3

How does galactose get into the cell?

Answer 3

Through a channel protein - galactoside permease

Question 4

What enzyme is needed to cleave lactose?

Answer 4

B-galactosidase

Question 5

What is the inducer for B-galactosidase?

Answer 5

Lactose

Question 6

What does the lac l gene code for?

Answer 6

Lac operon repressor - it is upstream of the lac operon

Question 7

What is an operon?

Answer 7

Genes of similar function that cluster together

Question 8

What does the lac z gene code for?

Answer 8

B-galactosidase

Question 9

What does the lac y gene code for?

Answer 9

galactoside permease

Question 10

Activator

Answer 10

A regulatory protein that binds to DNA and activates transcription. No to little transcription occurs without the activator present.

Question 11

Where does the repressor bind?

Answer 11

On the operator a little downstream of the promoter.

Question 12

How does lactose act as an inducer?

Answer 12

Binds to the repressor and causes it to release from the operator

Question 13

Inducer

Answer 13

Not a regulatory factor- removes repressor

Question 14

CAP - Catabolite Activator Protein

Answer 14

Activator for lac operon -binds to CAP binding site - strengthens the binding of RNA polymerase to the lac promoter

Question 15

cAMP

Answer 15

Only when CAP is bond to cAMP can it bind to DNA

Question 16

When are cAMP levels low?

Answer 16

When glucose levels are high. Thus, CAP isn’t active and transcription doesn’t occur

Question 17

How is cAMP inhibited?

Answer 17

Glucose inhibits adenylyl cyclase enzyme that phosphorylates cAMP