Structure of dna and replication2009


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Structure of dna and replication2009

  1. 1. Molecular Genetics IB Topic 4 (with a little 2 and 3 thrown in too)
  2. 2. DNA and DNA Replication It’s gonna be a cold, deadly winter !
  3. 3. The Hierarchy OF Genetic Material <ul><li>DNA – molecular, made up sugar, phosphate and bases. </li></ul><ul><li>Chromatin </li></ul><ul><ul><ul><li>“ chromosomes” in their natural state </li></ul></ul></ul><ul><ul><ul><ul><li>Made of DNA </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Made of proteins (HISTONES) </li></ul></ul></ul></ul><ul><ul><ul><li>Chromosomes – thickened, condensed chromatin – ready for mitosis or meiosis </li></ul></ul></ul><ul><ul><ul><li>Chromatid – 2 of the same chromosome doubled for reproductive purposes. (referred to as “sister”) </li></ul></ul></ul>
  4. 4. The Hierarchy OF Genetic Material <ul><li>Gene </li></ul><ul><ul><ul><li>an inheritable factor that controls a specific characteristic. </li></ul></ul></ul><ul><ul><li>Allele </li></ul></ul><ul><ul><ul><li>One specific form of a gene </li></ul></ul></ul><ul><ul><ul><li>Differs from other alleles by one or a few “bases.” </li></ul></ul></ul><ul><ul><ul><li>occupies the same gene locus as other alleles of that gene </li></ul></ul></ul><ul><ul><ul><li>dominant or recessive </li></ul></ul></ul><ul><li>Genome – the whole genetic information of an organism </li></ul>
  5. 5. How DNA was Discovered
  6. 6. James Watson (L) and Francis Crick (R), and the model they built of the structure of DNA DNA’s Dark Lady
  7. 7. Nucleic Acids <ul><li>1 st discovered in the nucleus </li></ul><ul><li>Building blocks (monomers) are nucleotides </li></ul><ul><li>Polymers are nucleic acids </li></ul><ul><li>Nucleotide = 5 carbon sugar, phosphate, and nitrogenous base. </li></ul><ul><li>Nucleic Acids are named for their SUGAR </li></ul><ul><ul><ul><li>2 Types – DNA and RNA </li></ul></ul></ul><ul><li>There is one LESS oxygen on the DNA Sugar. </li></ul>
  8. 8. DNA and RNA
  9. 9. The structure of DNA and RNA <ul><li>Genetic material of living organisms is either DNA or RNA. </li></ul><ul><li>DNA – Deoxyribonucleic acid </li></ul><ul><li>RNA – Ribonucleic acid </li></ul><ul><li>Genes are lengths of DNA that code for particular proteins. </li></ul>
  10. 10. DNA and RNA are polynucleotides <ul><li>Both DNA and RNA are polynucleotides. </li></ul><ul><li>They are made up of smaller molecules called nucleotides. </li></ul><ul><li>DNA is made of two polynucleotide strands: </li></ul><ul><li>RNA is made of a single polynucleotide strand: </li></ul>Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide
  11. 11. Structure of a nucleotide <ul><li>A nucleotide is made of 3 components: </li></ul><ul><li>A Pentose sugar </li></ul><ul><li>This is a 5 carbon sugar </li></ul><ul><li>The sugar in DNA is deoxyribose . </li></ul><ul><li>The sugar in RNA is ribose . </li></ul>
  12. 12. Structure of a nucleotide <ul><li>A Phosphate group </li></ul><ul><li>Phosphate groups are important because they link the sugar on one nucleotide onto the phosphate of the next nucleotide to make a polynucleotide. </li></ul>
  13. 13. Structure of a nucleotide <ul><li>A Nitrogenous base </li></ul><ul><li>In DNA the four bases are: </li></ul><ul><ul><li>Thymine </li></ul></ul><ul><ul><li>Adenine </li></ul></ul><ul><ul><li>Cytosine </li></ul></ul><ul><ul><li>Guanine </li></ul></ul><ul><li>In RNA the four bases are: </li></ul><ul><ul><li>Uracil </li></ul></ul><ul><ul><li>Adenine </li></ul></ul><ul><ul><li>Cytosine </li></ul></ul><ul><ul><li>Guanine </li></ul></ul>
  14. 14. Nitrogenous bases – Two types <ul><li>Pyrimidines </li></ul><ul><li>Thymine - T </li></ul><ul><li>Cytosine - C </li></ul><ul><li>Uracil - U </li></ul><ul><li>Purines </li></ul><ul><li>Adenine - A </li></ul><ul><li>Guanine - G </li></ul>
  15. 15. Adenine
  16. 16. Guanine
  17. 18. DNA Molecule
  18. 19. Sugar phosphate bonds (backbone of DNA) <ul><li>Nucleotides are connected to each other via the phosphate on one nucleotide and the sugar on the next nucleotide </li></ul><ul><li>A Polynucleotide </li></ul>
  19. 20. Base pairing <ul><li>The Nitrogenous Bases pair up with other bases. For example the bases of one strand of DNA base pair with the bases on the opposite strand of the DNA. </li></ul>
  20. 21. The Rule: <ul><li>Adenine always base pairs with Thymine (or Uracil if RNA) </li></ul><ul><li>Cytosine always base pairs with Guanine. </li></ul><ul><li>Bases are held together by weak hydrogen bonds (bonds between hydrogen and F, N, or O) </li></ul>
  21. 22. Complementary base pairing <ul><li>Purines Pyrimidines </li></ul><ul><li>Adenine Thymine </li></ul><ul><li>Adenine Uracil </li></ul><ul><li>Guanine Cytosine </li></ul>THE DNA Sequence Game - Wanna Play?
  22. 23. DNA and RNA Molecule
  23. 24. Draw on whiteboard
  24. 25. The Required Diagrams <ul><li>Molecular: </li></ul>
  25. 26. Simple Diagram
  26. 27. The Replication of DNA- THE S PHASE
  27. 28. My First You Tube Conversion Ever! Thanks, Josh!!!
  28. 29. Replication of DNA and Chromosomes <ul><li>Speed of DNA replication: 3,000 nucleotides/min in human 30,000 nucleotides/min in E.coli </li></ul><ul><li>Accuracy of DNA replication: Very precise (1 error/1,000,000,000 nt) </li></ul>
  29. 31. Replication DNA Replication – Ann’y
  30. 33. DNA REPLICATION OVERVIEW <ul><li>Involves 20 different enzymes and other proteins. </li></ul><ul><li>IN THREE MAJOR STEPS: (S PHASE) </li></ul><ul><li>1. </li></ul><ul><ul><li>Enzymes attach to existing DNA </li></ul></ul><ul><ul><li>Break Hydrogen Bonds between base pairs </li></ul></ul><ul><li>2. </li></ul><ul><ul><li>Double Helix unwinds(TEMPLATE for new bases) </li></ul></ul><ul><ul><ul><li>Enzyme - Helicase </li></ul></ul></ul><ul><li>3. </li></ul><ul><ul><li>NEW AND MATCHING strand is SYNTHESIZED for each existing strand. </li></ul></ul><ul><ul><ul><li>DNA POLYMERASE – enzymes that carries out replication of strand. </li></ul></ul></ul><ul><ul><ul><li>Work in ONE direction </li></ul></ul></ul><ul><ul><ul><li>Work from opposite ends of strands. </li></ul></ul></ul>
  31. 34. Replication as Semi Conservative <ul><li>DNA Replication is thought to be semi-conservative. </li></ul><ul><ul><li>Uses ½ of the parent strand as ½ of the new daughter strands. </li></ul></ul><ul><ul><li>“ Conserves” the need for the production of new bases. </li></ul></ul><ul><ul><li>The parent strand is the template that adds complementary bases. </li></ul></ul>
  32. 35. Semi-Conservative Replication
  33. 36. Simplified illustration of replication <ul><li>The two strands of DNA separate from one another </li></ul><ul><li>Each strand serves as a template (model) for a new strand </li></ul><ul><li>Each new DNA molecule consists of one old strand and one new strand </li></ul>
  34. 37. The Role of Enzymes <ul><li>Helicase – </li></ul><ul><ul><li>Unwinds and separates the DNA molecule </li></ul></ul><ul><ul><li>Allows for replication enzymes to attach </li></ul></ul><ul><li>Polymerase(s) </li></ul><ul><ul><li>More than one </li></ul></ul><ul><ul><li>Links the phosphate of the new nucleotide to the sugar of the nucleotide by a covalent bond </li></ul></ul>
  35. 42. Replication Forks
  36. 43. Replication Forks <ul><li>Areas where DNA double strands have been “unzipped” for replication to occur. </li></ul>
  37. 46. Mutations <ul><li>DNA in a typical animal cell has about 3 billion nucleotide pairs. (6 billion nucleotides) </li></ul><ul><li>An “error” occurs approximately in every 1000 nucleotides. These errors are usually repaired…leaving about 1 error in about 1 billion nucleotides. </li></ul><ul><li>An error that remains is a mutation and can be harmful or lethal. </li></ul>
  38. 48. Table from Biological Science – Green, Stout, Taylor