Chapter 11: The control of gene expression

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Chapter 11 The control of gene expression
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Look at turning on and off genes

• Eukaryotes
• Many examples
• Reproductive and therapeutic cloning
• Prokaryotes
• Operons
• Promoter, Operator, Set of genes

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Cloning

• Reproductive cloning
• Produce new individuals
• Ethical issues
• Therapeutic cloning
• Harvest embryonic stem cells in an effort to
  treat various diseases
• Medical potential

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Cloning

• Making multiple copies of one thing
• That thing may be different in different
  situations

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Cloning

• Mitosis
• Results in genetically identical daughter cells
  (clones)
• Twins
• An embryo is split producing two identical
  embryos (clones)
• Genetic cloning
• Recombinant DNA putting the DNA of one organism
  into the genome of another organism
• Reproductive cloning
• Therapeutic cloning

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Reproductive cloning

• Individual created by asexual reproduction
• Genetically identical to a single parent

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In 1996, the first cloned sheep (Dolly) produced
by stem cell nuclear transplant
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Cloned animals

• The first Dolly Sheep
• Other cloned animals
• Horses
• Cats
• Cows
• Goats
• Pigs
• Monkeys
• Mice
• Dogs

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Somatic cell nuclear transfer
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Cloning

• http//www.vtaide.com/png/cloning.htm
• Click on click and clone
• Click on is it cloning or not

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This technology can be used for both reproductive
and therapeutic cloning
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• http//www.vtaide.com/png/cloning.htm
• Click on clone zone therapeutic or reproductive
• Click on cloning poster

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Uses of reproductive cloning

• Advantages
• Slow extinction of species
• Repopulate endangered species

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Uses of reproductive cloning

• Disadvantages
• Limits genetic diversity
• Problem to endangered species
• Cloned animals less healthy than those arising
  from a fertilized egg
• To create the perfect race

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Therapeutic cloning
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Embryonic stem cells

• Cells in the early embryo that can differentiate
  and give rise to all cells in the body
• They can divide indefinitely like cancer cells
• Certain growth factors can induce changes in gene
  expression that cause differentiation into a
  specific cell type

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ES cells can differntiate into specific cell
types under the right growth conditions
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• http//www.vtaide.com/png/cloning.htm
• Click on cloning quiz

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Cloning development of a multicellular organism

• Depends on turning on and off genes
• Control of gene expression

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Terms that you will need to know

• DNA
• mRNA
• Transcription
• Translation

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How do bacteria control transcription

• Use an operon
• A DNA sequence having
• A group of genes
• A promoter
• An operator

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Example Lac operon

• Lactose Sugar
• Bacteria can use it for food
• Need three enzymes
• Inefficient to make enzymes when it is not needed

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What does the Lac operon do?

• It regulates transcription of lactose-digesting
  enzyme genes
• It transcribes enzyme RNA when lactose is present
• It shuts down transcription when lactose is not
  present and does not need to be broken down

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Parts of the Lac Operon

• RNA polymerase
• The enzyme which makes the RNA (transcription)
• Promoter
• A region on the DNA where the RNA polymerase can
  attach and initiate transcription
• Operator
• A region on the DNA next to the promoter where
  the repressor binds
• The repressor binds to the operator when lactose
  is absent
• When you do not want to break down lactose
• The repressor cannot bind to the operator when
  lactose is present, when RNA polymerase binds to
  the promoter
• When you want to break down lactose

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What happens when the Lac operon is off?
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What happens when the Lac operon is on?