2. Genetic Control


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2. Genetic Control

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