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Gene Expression - PowerPoint PPT Presentation


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Gene Expression. Why Regulate Gene Expression?. Response to changing developmental or environmental conditions Save… time energy raw materials. Feedback Inhibition Product inhibits enzyme function Regulation of transcription Product inhibits enzyme production. Prokaryotic Regulation.

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Presentation Transcript
why regulate gene expression
Why Regulate Gene Expression?
  • Response to changing developmental or environmental conditions
  • Save…
    • time
    • energy
    • raw materials
prokaryotic regulation
Feedback Inhibition

Product inhibits enzyme function

Regulation of transcription

Product inhibits enzyme production

Prokaryotic Regulation
slide4

Research and

Development

Testing

Production

Distribution

Drug Company

MGMT

operon regulation
Operon Regulation

Inducible

Repressible

Default on

Repressor inactive

Turned off when product is present

Repressor active

Default off

  • Repressor active

Turned on when substrate is present

  • Repressor inactive
inducible operon
Inducible Operon

Substrate Absent

  • Repressor protein binds to operator
  • Operon blocked
  • No substrate-catabolizing enzymes produced

Default: OFF

Substrate Present

  • Substrate inactivates repressor protein
  • Operon transcribed
  • Enzymes produced

RG

P

O

1

2

3

RNAPoly

repressible operon
Repressible Operon

Product Absent

  • Repressor protein inactive
  • Operon transcribed
  • Product-anabolizing enzymes produced

Default: ON

Product Present

  • Product activates repressor protein
  • Operon blocked
  • No enzymes produced

RG

P

O

1

2

3

RNAPoly

inducible repressible both or neither
Inducible, Repressible, Both, or Neither?
  • The Lac operon
  • Regulatory gene codes for repressor protein
  • Operon expressed (ON) by default
  • Substrate inactivates repressor protein
  • Product binds to RNA polymerase
  • Product activates repressor protein
  • Repressor protein status changes when bound by particles
  • Enzymes deactivate repressor protein
  • The Trpoperon
  • Operon blocked (OFF) by default
  • Active repressor protein blocks transcription
  • Repressor is created in an active state
inducible repressible both or neither1
Inducible, Repressible, Both, or Neither?
  • The Lac operon I
  • Regulatory gene codes for repressor protein B
  • Operon expressed (ON) by default R
  • Substrate inactivates repressor protein I
  • Product binds to RNA polymerase N
  • Product activates repressor protein R
  • Repressor protein status changes when bound by particles B
  • Enzymes deactivate repressor protein N
  • The Trpoperon R
  • Operon blocked (OFF) by default I
  • Active repressor protein blocks transcription B
  • Repressor is created in an active state I
eukaryotic regulation
Eukaryotic Regulation
  • Tend to have 10x the genes of prokaryotes
  • Expression is controlled at multiple points
chromatin modification
Heterochromatin

Partially coiled

Euchromatin

Uncoiled

Chromatin Modification
chromatin modification1
Chromatin Modification
  • Methylation
    • Attachment of methyl groups to cytosine
  • HistoneAcetylation
    • Attachment of acetyl groups to histones
    • Loosens grip of histones on DNA
post transcriptional regulation1
Post-transcriptional Regulation
  • RNA Degradation
  • Translation Blockage
  • Protein Degradation
tumor supressor genes
Code for proteins that inhibit division

(Including density & anchorage dependence)

Tumor Supressor Genes

Tumor Supressor Gene

Deletion

carcinogenic viruses
Some viruses donate their genetic material

Provirus may

include an oncogene

disrupt an tumor supressorgene

make a promotor more active

Carcinogenic Viruses

Promoter

Gene

review questions
Review Questions

Use no more than 1 word for each answer.

  • What type of organic molecule is a histone?
  • What is the structural difference between heterochromatin and euchromatin?
  • What does a proteasome do?
  • When expressed, what type of gene causes a cell to divide when it normally would not?