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Flashcards in Lac Operon Deck (13):
1

Define

 

 

Promoter

a specific segment of DNA that binds with RNA Polymerase to begin transcription of mRNA from the operon genes

2

Define

 

Operator

sequence of nucleotides located between the promoter and structural genes where the repressor protein can bind

3

Define

 

Regulator

 

sequence of DNA found anywhere on the bacterial chromosome; codes for the production of repressor protein. Is not part of the operon.

4

Define

 

Inducer

 

substance which can activate or inactive a repressor  (Lactose)

5

Lac Operon

  • In the case of the lac operon, lactose is the _____.
  • If lactose is present, it binds to and _____ the repressor by causing it to fall off the operator.
  • If lactose operator is free of the repressor, then __________ is able to bind.
  • If RNA Polymerase can bind to the lac operon, then __________ is produced, and _____ is catabolized into glucose and galactose for energy.
  • __________ is also produced, which allows more lactose to enter the cell.

Lac Operon

  • In the case of the lac operon, lactose is the inducer.
  • If lactose is present, it binds to and inactivates the repressor by causing it to fall off the operator.
  • If lactose operator is free of the repressor, then RNA Polymerase is able to bind/continue in the sequence.
  • If RNA Polymerase can bind to the lac operon, then B-galactosidase is produced, and lactose is catabolized into glucose and galactose for energy.
  • Permease is also produced, which allows more lactose to enter the cell.

6

  • How is the lac operon induced?
     
  • How is it "uninduced"?

  • How is the lac operon induced?
    • The operon is induced when lactose molecules bind to the repressor protein.
    • As a result, the repressor protein loses its shape and falls off of the operator region.
    • Therefore, RNA polymerase can continue transcribing the rest of the operon. 
  • How is it "uninduced"?
    • After all of the lactose is gone from the environment or glucose threshold is reached, then the repressor protein regains its shape and goes back to the operator region.
    • Then, it blocks RNA polymerase from transcribing the genes that produce B-galactosidase , acetylase, and permease.

7

Define

 

Operon

groups of closely related genes coding for enzymes or other proteins that are all controlled by one promoter

8

  • ________ of the operon is controlled by the presence or absence of a regulatory protein bound to the operator

  • Transcription of the operon is controlled by the presence or absence of a regulatory protein bound to the operator

9

How is the repressor to the lac operon allosterically controlled?

  • (+)
    • Glucose
  • (-)
    • Lactose binds to the repressor and changes its conformation so it won't bind to the operator 

10

What are the 3 molecules necessary for the transcription of the lac operon?

  • CAP
     
  • Sigma Factor
     
  • RNA polymerase

11

Do bacteria have introns?

No, because there is a pressure (genome streamlining.

12

In what type of RNA does spicing happen?

pre mRNA

13