33. POSITIVE GENE REGULATION

Question 1

1. What is Positive Gene regulation?

Answer 1

• this is when Operons are switched on
• they are switched on by an active form of the activator

Question 2

2. What is the Activator of Transcription?

Answer 2

• any kind of stimulatory protein

Question 3

3. Give an example of an Activator of Transcription.

Answer 3

• Catabolic Activator Protein (CAP)
• this is found in E.Coli
• this enhances the transcription of the Lac Operon

Question 4

4. What is an example of Positive gene regulation when it comes to the Lac Operon?

Answer 4

• absence of glucose
• this further stimulates transcription

Question 5

5. What is constantly present in Glycolysis?

Answer 5

• the enzymes that break down Glucose

Question 6

6. What will E.coli do when both glucose and lactose are present?

Answer 6

• it will use glucose rather than lactose
• this is because there are low quantities of glucose
  enzymes needed to breakdown lactose
• this is known as normal low transcription

Question 7

7. When does E.coli use lactose instead of glucose?

Answer 7

• when lactose is present
• when glucose is in short supply
• E.COLI WILL USE LACTOSE AS AN ENERGY SOURCE:
  
  • it will then synthesise the enzymes that are needed
    for lactose breakdown
  • it will synthesise a much larger quantity
  • this is known as Enhanced Transcription

Question 8

8. List 3 characteristics of Low Glucose levels.
   (the lactose is present in this situation)

Answer 8

1. Increases in levels of cAMP
2. The Carboxylic Activator Protein is acivated
   
   • this happens when it is binded to the cAMP
3. THE ACTIVATED CARBOXYLIC ACTIVATOR PROTEIN
   
   • attaches to the promoter of the Lac Operon

Question 9

9. What happens when the Activated Carboxylic Activator Protein attaches to the promoter of the Lac Operon?

Answer 9

• this increases the affinity of the RNA polymerase
• this accelerates the transcription of the Lac Operon
• more proteins and enzymes involved in hydrolysis are
  produced

Question 10

10. List 3 characteristics of High Glucose Levels?

Answer 10

1. Decrease in the levels of cAMP
2. Carboxylic Activator Protein detaches from the Lac
   Operon
3. There is a decreased affinity for RNA Polymerase
   - there is low transcription of the Lac Operon
   - less genes and enzymes produced that are invplved in
   Lactose hydrolysis

Question 11

11. What is the Lactose hydrolysed to?

Answer 11

• Galactose
• Glucose