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2. Genetic Control

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2. Genetic Control 2. Genetic Control Presentation Transcript

  • Genetic Control SQA HIGHER BIOLOGY Control & Regulation
  • What types of cells are these? What causes them to be different?
  • What’s going on here? What controls all of this? View slide
  • Learning Content
    • Genetic control.
      • An introduction to the Jacob-Monod hypothesis of gene action in bacteria.
      • The part played by genes in controlling metabolic pathways as shown in the case of phenylketonuria.
      • The control of cell differentiation by switching particular genes on or off.
    View slide
  • Revision
    • What is a gene?
      • What does it consist of?
      • What does it do?
      • How does it do this?
  • Lactose Digestion
    • What is lactose?
    • What catalyses the breakdown of lactose?
  • Gene Action in Bacteria
    • What do E.coli need glucose for?
    • If E.coli encounters the sugar lactose, what does it need to do to it before it can respire?
    • What type of molecule is β -galactosidase?
      • How would this be made?
    • The gene for β -galactosidase is only switched on in the presence of lactose.
      • Why would it be advantageous for E.coli not to produce β -galactosidase all of the time?
      • What is this process called?
      • How does it work?
  • Gene Action in Bacteria
    • The structural gene which codes for β -galactosidase in E.coli is not alone.
      • It is alongside an operator gene – this controls the structural gene.
      • These two genes are known as an operon.
    • There is also a regulator gene nearby – this produces a repressor molecule which affects the operator gene.
    Repressor molecule β -galactosidase
  • Gene Action in Bacteria
    • The regulator gene continually produces the repressor molecule.
    • Use the cut and stick sheet to represent what occurs in the operon in the absence of lactose.
    Regulator gene produces repressor molecule Repressor binds to operator Structural gene switched off, no β -galactosidase produced
  • Gene Action in Bacteria
    • Use the remaining of the cut & stick sheet to show what happens when lactose is present.
    Repressor molecule binds with lactose Operator free so structural gene switched on, β -galactosidase produced What will happen once all of the lactose is broken down?
  • Gene Action in Bacteria
    • Annotate your diagram with notes from page 237:
      • What advantage does this system provide for E.coli ?
      • What is meant by the term ‘inducer’? What is the inducer in this example?
      • Who proposed this hypothesis?
  • Phenylketonuria
    • Define the following terms:
      • Metabolism
      • Metabolic pathway
    • What controls each step in a metabolic pathway?
    • Explain how a gene mutation could interfere with a metabolic pathway.
    • Even if you have a mutated gene, why is it possible for you to have a normal phenotype?
    • How can someone suffer from an inborn error of metabolism?
  • Phenylketonuria
    • What are phenylalanine and tyrosine?
    • Where do we get them from?
    • What is phenylketonuria (PKU)?
    • What are the effects of PKU on the sufferer?
    phenylalanine tyrosine intermediate melanin other metaobolites (e.g. thyroxine) enzyme 1 enzyme 2 enzyme 3 other enzymes
  • Phenylketonuria
    • How is phenylketonuria screened for?
    • How can it be treated?
  • Albinism
    • What causes albinism?
    • What effects does this have on a sufferer?
  • Differentiation
    • What does differentiation mean?
    • Can differentiation be reversed? Can a specialised cell change? What makes this difficult?
  • Genetic Control of Differentiation
    • Genes in a differentiated cell can either be described as being switched on or off, explain what this means.
    • Name some examples of genes which would be switched on in all cells.
    • Name some examples of genes which would be switched on in only some cells.
    • Summarise the formation of differentiated blood cells and parenchyma cells.
    • How is leaf shape an example of genetic control?