Gene Cloning Very Detailed Antibiotic Resistance


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Gene Cloning Very Detailed Antibiotic Resistance

  1. 1. DNA Replication <ul><li>Converting a single DNA helix into two identical copies. </li></ul><ul><li>Described as semi conservative replication . </li></ul>
  2. 2. New DNA Strands <ul><li>Helicase enzyme splits and unwinds the two stranded DNA. </li></ul>3’ 5’
  3. 3. Naming DNA Direction <ul><li>DNA strands are recognised and named according to the carbon atom exposed at the end of the strand. </li></ul>C 5 C 1 C 2 C 3 C 4
  4. 4. Forming a New Strand <ul><li>An enzyme RNA polymerase is used to add a short section of RNA to start the process. </li></ul><ul><li>A topoisomerase enzyme cuts the DNA strand allowing it to twist and relieve pressure. </li></ul>3’ 5’ 3’ 5’
  5. 5. Addition of nucleotides <ul><li>When nucleotides are added to a new strand they can only do so in a 5’ (5 prime) to 3’ direction. </li></ul>3’ 5’ 3’ 5’ <ul><li>An enzyme DNA polymerase III is used to catalyse the addition of DNA nucleotides. </li></ul>
  6. 6. Base Pairing <ul><li>Nucleotides are added. A joins to T, C joins to G. </li></ul>T C G G C A T C G G A T A T T G A A C C T G A G C A T C G C A T C
  7. 7. New DNA Strands <ul><li>The leading strand (red) is synthesised continuously. </li></ul><ul><li>The lagging strand (pink) is formed in segments called okazaki fragments. </li></ul><ul><li>An enzyme DNA polymerase I replaces the RNA primers with DNA </li></ul>3’ 5’ 3’ 5’
  8. 8. Filling the Gaps <ul><li>An enzyme DNA Ligase is used to fill in the gaps in the okazaki fragments with nucleotides. </li></ul><ul><li>The DNA strands continue to form in a 5’ to 3’ direction. </li></ul>3’ 5’ 3’ 5’
  9. 9. Completion <ul><li>When DNA replication is complete two molecules are formed. </li></ul><ul><li>Because half of each strand is new and half original it is called semi conservative replication. </li></ul>
  10. 10. Questions <ul><li>What is the purpose of DNA replication? </li></ul><ul><li>Converting a single DNA helix into two copies. </li></ul><ul><li>Name the enzyme that splits and unwinds DNA. </li></ul><ul><li>Helicase. </li></ul><ul><li>Why is the 5’ end of a DNA strand given this name? </li></ul><ul><li>The carbon in the number 5 positions of the sugar unit is the one exposed. </li></ul><ul><li>What is the role of the topoisomerase enzyme? </li></ul><ul><li>To cut the DNA strand and allow it to twist and relieve pressure. </li></ul>
  11. 11. Questions continued <ul><li>How is the addition of nucleotides started? </li></ul><ul><li>An enzyme RNA polymerase adds a short section of RNA. </li></ul><ul><li>What is the role of DNA polymerase III ? </li></ul><ul><li>It catalyses the addition of DNA nucleotides. </li></ul><ul><li>In what direction are nucleotides added? </li></ul><ul><li>5’ to 3’ </li></ul><ul><li>What are the base pairing rules? </li></ul><ul><li>A joins with T and C joins with G. </li></ul><ul><li>Why does this occur? </li></ul><ul><li>A and T form double bonds while C and G form triple bonds. </li></ul>
  12. 12. Questions continued <ul><li>What name is given to the continuously formed strand? </li></ul><ul><li>Leading strand. </li></ul><ul><li>Why is the lagging strand formed in fragments? </li></ul><ul><li>As the helicase enzyme moves it only exposes a small section of DNA and because DNA forms 5’ to 3’ it does so in sections. </li></ul><ul><li>What name is given to the DNA fragments? </li></ul><ul><li>Okazaki fragments. </li></ul><ul><li>Which enzyme joins the fragments together? </li></ul><ul><li>DNA ligase. </li></ul>