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DNA

DNA. A Few Questions. How did we get to know about DNA? What is DNA? What does DNA stand for? What does DNA look like? How is it created? What makes DNA? Where does it happen? How do we look at DNA?. Draw a structure of DNA. Griffith and Transformation. 1928- British Scientist:

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DNA

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  1. DNA

  2. A Few Questions • How did we get to know about DNA? • What is DNA? • What does DNA stand for? • What does DNA look like? • How is it created? • What makes DNA? • Where does it happen? • How do we look at DNA?

  3. Draw a structure of DNA

  4. Griffith and Transformation • 1928- British Scientist: • Problem: how bacteria makes people sick? • Studied pneumonia on mice • Looked at 2 strains of bacteria: harmless and diseased • Results: • Mice injected with diseased= death • Mice injected with harmless = life • Heated up diseased injected into mice and life • Lead him to his theory of transformation

  5. Transformation • He mixed heated killed disease bacteria, with harmless ones--- into mice= mice death. • How did it happen? • Somehow the disease causing bacteria passed their ability into the healthy bacteria resulting in diseased bacteria. • =Transformation: one strain changed permanently into another. • Information was transferred: • What information was transferred? • Genes==========

  6. Avery and DNA • 1944: Canadian biologist • Repeated Griffith’s work • Problem: Which molecule was important in the transformation? • Did same experiment except before injected mice added chemical to kill, carbs, proteins, lipids, nucleic acid RNA, and other molecules • =death

  7. Continued….. • Next added enzyme to kill DNA • Result===== life • Concluded: • Discovered that the nucleic acid DNA stores and transmits the genetic info form 1 generation of an organism to the next.

  8. Hershey/Chase • Challengers: • 1952 • Studied viruses that infect living organisms. • Looked at bacteriophages: • Composed of DNA or RNA core and a protein coat Video Concluded: that the genetic materia of the bacteriophage was DNA, not protein.

  9. DNA Facts! DNA is too small to see, but under a microscope it looks like a twisted up ladder! DNA stands for:D: DeoxyriboseN: NucleicA: Acid Every living thing has DNA. That means that you have something in common with a zebra, a tree, a mushroom and a beetle!!!!

  10. DNA • Is a nucleic acid • Usually in the form of a double helix • established by James Watson and Francis Crick

  11. Components of DNA • Nucleic Acid: macromolecule composed of nucleotide chains that convey genetic material Nucleotide: long chains of chemical units

  12. Components of DNA • The DNA nucleotide is made up of three parts • Phosphate group • Nitrogenous base • Sugar (Deoxyribose)

  13. Phosphate group • Phosphorous: consists of 1 phosphate and 4 oxygen

  14. Sugar (Deoxyribose) • A five carbon sugar that connects the phosphate group and the nitrogenous base

  15. Sugar-Phosphate Backbone • Nucleotides are joined by covalent bonds between the sugar of one nucleotide and the phosphate of the next • Sugar-Phosphate Backbone: a repeating pattern of S-P-S-P

  16. Sugar-Phosphate Backbone

  17. Components of DNA • Deoxyribose: a monosaccharide containing five carbon atoms

  18. Nitrogenous Bases • The four nucleotides found in DNA are only different because of their nitrogenous bases • Thymine (T) • Cytosine (C) • Adenine (A) • Guanine (G)

  19. Two Types of Bases • Pyrimidines: single ring structures • Thymine (T) • Cytosine (C) • Purines: larger, double ring structures • Adenine (A) • Guanine (G)

  20. Draw the DNA Nucleotide • Remember the three parts of DNA

  21. DNA is like a ladder with steps and rails. This is a rail This is a step Green can only go with Red Purple can only go with Yellow

  22. DNA as a Rope Ladder • The rails of the ladder consist of: • Deoxyribose • Phosphate group • The Steps of the ladder consist of: • Nitrogenous bases (A, T, C, G)

  23. Since DNA is a Double Helix… • The steps of the ladder are connected by the nitrogenous bases: • They are connected by hydrogen bonds • T bonds with A • C bonds with G

  24. Try to draw the Double Helix

  25. Review • Draw the three components of the DNA nucleotide • Label the 5 carbons

  26. Animation • http://www.teachertube.com/view_video.php?viewkey=a9fe76d6b3f30f02150b&page=1&viewtype=&category=

  27. DNA Replication

  28. DNA Replication • Replication begins with the untwisting of the double helix • This untwisting is the two strands of parental DNA • The two strands become the template for replication

  29. DNA Replication

  30. DNA Replication • The nucleotides line up along the template strand • In accordance with the base-pairing rules • Enzymes then link the nucleotides to form the new DNA stands

  31. DNA Replication • The new DNA strands are called daughter DNA strands • Identical molecules of the parent DNA • The enzymes that link the nucleotides to the daughter strands are called DNA polymerases

  32. Daughter strands

  33. Potential Problems in Replication • The helical DNA molecule must untwist as it replicates • And must copy its two strands almost simultaneously • The speed of the process is a challenge • Nucleotides are added at a rate of 50/second in mammals • Added at a rate of 500/second in bacteria

  34. DNA Polymerase • Adds nucleotides only to the 3’ end of the strand • Never to the 5’ end • So, a daughter strand can only grow in the 5’ to 3’ direction

  35. Daughter DNA strands • One of the daughter strands can be synthesized in one continuous piece • Working toward the forking point of the parental DNA • The other daughter strand is synthesized in pieces • DNA ligase ties (ligates) those pieces together

  36. Why is DNA replication important??? • Ensures multicellular organisms carry the same genetic information • This also means our genetic instructions are copied for the next generation of the organism

  37. DNA Replication

  38. Replication works like this…..

  39. Begin to bind and results in two new strands.

  40. http://www.ncc.gmu.edu/dna/repanim.htm • http://www.wiley.com/legacy/college/boyer/0470003790/animations/replication/replication.htm

  41. Why is DNA replication amazing? • It requires the cooperation of more than a dozen enzymes and other proteins • It is extremely accurate • About 1 in 1,000,000,000 nucleotides in DNA are incorrectly paired • DNA polymerases carry out a proofreading step to remove nucleotides that have base-pairs incorrectly matched

  42. DNA Replication • Draw the process of replication • Label all the steps and structures of DNA replication

  43. You can tell people apart by their fingerprints… Because everyone’s fingerprints are different!

  44. DNA is like a fingerprint because everyone’s is a little different! How does the police look at DNA to figure out who committed a crime?

  45. STEP # 1 The DNA gets cut up by special scissors!!!

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