32. INDUCIBLE OPERONS

Question 1

1. What is a Lac Operon?

Answer 1

• this is an inducible operon
• it contains genes that code for enzymes
• these enzymes are used in Lactose Metabolism
  (Hydrolysis)

Question 2

2. What can be said about the state of Transcription for an Induced Operon?

Answer 2

• the Transcription is normally off
• it can be activated and induced
• this is done by a small lactose molecule that binds
  allosterically to the regulatory protein

Question 3

3. What happens when the Lactose is absent?

Answer 3

• the Lac Operon is inactivated
• the Lac repressor is active by itself
• the Lac repressor will bind to the operator
• the Lac operon is inactivated
• RNA polymerase can not transcribe the genes involved
  in Lactose metabolism
• the lactose hydrolysis stops

Question 4

4. What happens when the Lactose is present?

Answer 4

• Lac Operon is activated
• we have an inducer present
• there is also an Allolactose present

Question 5

5. What is the Inducer in this case?

Answer 5

• this is a molecule
• it is called Allolactose
• it binds to the repressor
• it inactivates the repressor
• this turns the Lac Operon on

Question 6

6. What is the Allolactose in this case?

Answer 6

• this is a disaccharide
• it is similar to lactose
• it is an isomer of lactose

Question 7

7. What does the Allolactose consist of?

Answer 7

• it consists of Monosaccharides
• these are called D-galactose and D-glucose
• they are linked through a Beta 1-6 glycosidic linkage
  (instead of a beta 1-4 linkage)

Question 8

8. What does it mean when the Lac Operon is on?

Answer 8

• the genes that code for specific enzymes are
  transcribed
• these enzymes assist in Lactose Hydrolysis

Question 9

9. When does Lactose Hydrolysis start?

Answer 9

• it starts when the Lactose is broken down into
  galactose and glucose