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MED 109- BIOLOGY II > 31. REGULATION OF GENE EXPRESSION > Flashcards

31. REGULATION OF GENE EXPRESSION Flashcards

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1
Q
  1. What do Prokaryotes and Eukaryotes change their gene expression according to?
A
  • they change it according to their environmental
    changes
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2
Q
  1. What does gene expression regulate in multicellular eukaryotes?
A

-it regulates development
- it is responsible for the differences between different
types of cells
- this is known as cell specialisation

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3
Q
  1. What do RNA molecules do?
A
  • they play a role in regulating the gene expression of
    the eukaryote
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4
Q
  1. What has natural selection favoured bacteria to produce?
A
  • they produce only the products that they need
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5
Q
  1. In which 2 ways can Bacteria regulate their metabolic pathways?
A
  1. REGULATION OF ENZYME ACTIVITY
    • this is done by feedback inhibition
  2. REGULATION OF ENZYME PRODUCTION
    • this is done by gene expression
    • it is controlled by Operons
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6
Q
  1. What is an Operon?
A
  • this is a prokaryotic DNA segment
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7
Q
  1. What do Operons consist of?
A
  • the operator
  • the promoter
  • a group of functionally related genes
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8
Q
  1. What is an Operator?
A
  • this is a segment of DNA
  • it works as a regulatory on and off switch
  • it controls the clustered functionally related genes
  • it consists of a specific sequence

THIS SPECIFIC SEQUENCE IS FOUND:
- within a promoter of these genes

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9
Q
  1. What is a Repressor?
A
  • this is a protein
  • it switches off the Operon
  • this prevents gene transcription
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10
Q
  1. How does the Repressor switch off the Operon?
A
  • it does this by binding to the Operator
  • it then blocks the RNA Polymerase binding
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11
Q
  1. What produces the Repressor?
A
  • a separate regulatory gene
  • a repressor can be in an active or inactive form
  • this depends on the presence of other molecules
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12
Q
  1. What is a Co-Repressor?
A
  • this is a molecule
  • it co-operates with the repressor protein
  • it helps it to switch off the Operon
    and to inactivate the Operon
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13
Q
  1. What is Negative Gene regulation?
A
  • this is when the Operon is switched off
    by an ACTIVE form of the Repressor
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14
Q
  1. List 3 characteristics of Repressible Operons?
A
  1. THEY ARE USUALLY ACTIVE
  2. THEY USUALLY REGULATE
    • a gene expression of enzymes
      - these are involved in anabolic pathways
  3. THEIR SYNTHESIS IS REPRESSED
    • it is repressed by high levels of the end product
    • this end product is known as the Co-repressor
    • this co-repressor activates the repressor
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15
Q
  1. Give an example of a Repressible Operon?
A
  • the trp Operon
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16
Q
  1. List 3 characteristics of Inducible Operons?
A
  1. THEY ARE USUALLY INACTIVE
  2. THEY USUALLY REGULATE
    • a gene expression of enzymes
      - these are involved in catabolic pathways
  3. THEIR SYNTHESIS IS INDUCED
    • it is induced by a chemical signal
    • this is known as the Inducer
    • this inducer activates the repressor
17
Q
  1. Give an example of an Inducible Operon?
A
  • Iac Operon
18
Q
  1. What can synthesise the amino acid names Tryptophan?
A
  • E coli
19
Q
  1. What is the trp Operon?
A
  • this operon contains genes of enzymes
  • these enzymes are involved in the synthesis of
    Tryptophan
20
Q
  1. When it comes to a Repressible Operon, what can be said about the state of Transcription?
A
  • Transcription is normally on
  • this transcription can be inhibited and repressed
  • this is done with a small molecule of Tryptophan
  • this tryptophan binds allosterically to the regulatory
    protein
21
Q
  1. What happens when the Tryptophan is absent?
A
  • the trp Operon is activated
  • the repressor is inactive
  • the repressor cannot bind to the operator
  • the genes for the enzymes required for tryptophan are
    transcribed
  • tryptophan production starts
22
Q
  1. What happens when the Tryptophan is present?
A
  • the trp Operon is inactivated
  • the trp is a corepressor
  • this means that it will bind to the trp repressor protein
  • the repressor is activated
  • the repressor binds to the Operator
  • the trp operon is inactivated
  • tryptophan production stops
23
Q
  1. When is the repressor active?
A
  • only in the presence of the corepressor Tryptophan
24
Q
  1. What happens if Tryptophan levels are high?
A
  • the trp Operon will be repressed
  • it will be turned off

MED 109- BIOLOGY II (90 decks)

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