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Structure of DNA

Structure of DNA. Do Now. Read and React 10 minutes to Read and React with 10 lines. Homework. Define (Page 362-365) RNA Messenger RNA Ribosomal RNA Transfer RNA Transcription RNA polymerase Promoter Intron Exon. Review Homework.

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Structure of DNA

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  1. Structure of DNA

  2. Do Now • Read and React • 10 minutes to Read and React with 10 lines

  3. Homework • Define (Page 362-365) • RNA • Messenger RNA • Ribosomal RNA • Transfer RNA • Transcription • RNA polymerase • Promoter • Intron • Exon

  4. Review Homework • List the conclusions that Griffith and Avery drew from their experiments? • Griffith concluded that heritable substance transforms harmless bacteria into harmful bacteria. Avery found this is DNA

  5. Review Homework • What was the experimental variable that Avery used when he repeated Griffith’s work? • Molecule-destroying enzyme he used

  6. Review Homework • What conclusions did Hershey and Chase draw from their experiments? • DNA is the genetic material found in genes

  7. Components of DNA • What does DNA stand for? • Deoxyribonucleic acid • Made up of nucleotides joined into long strands and chains • Made up of 5 carbon sugar called deoxyribose and phosphate • Has 4 nitrogen bases: adenine, guanine, cytosine and thymine • Commonly referred to as A, G, C, T

  8. Components of DNA • Nitrogen bases are bases that contain nitrogen • These bases stick out sideways from each other • Can be joined in any order

  9. Structure of DNA • Erwin Chargaff • Showed percentages of adenine and thymine are almost always identical in DNA • Percentages of Guanine and Cytosine are also almost identical • What conclusion would you draw from this? • A=T • G=C

  10. Structure of DNA • Rosalind Franklin • Took x-ray diffraction pictures that revealed the double-helix structure of DNA • Only showed a 2-D model of DNA, but presents in X-shape • James Watson and Francis Crick • Built a model of the DNA molecule that explained both structures and properties of DNA • Used Franklin’s x-shape to discover Double-Helix

  11. The Double Helix • The double helix explains Chargaff’s rule of base pairing • Model shows: • 2 strands in double helix run in opposite directions with bases in the center • Each strand carries a sequence of nucleotides, arranged like letters of alphabet for recording genetic info • Hydrogen holds strands together • Chemically speaking, H bonds strong or weak? • H bonds form only between pairs (AT – CG) • Base Pairing

  12. The Double Helix • Like a twisted ladder or a spiral staircase • Each strand is “antiparallel” • Antiparallel? • Run in opposite directions

  13. Base Pairing • The perfect fit of Adenine with Thymine • Guanine and Cytocine • Why are the weak Hydrogen bonds important? • Think of the functions of DNA

  14. Final Questions • Why did scientists have to resort to methods other than a microscope? • Explain the idea of base pairing?

  15. Homework • Define (Page 362-365) • RNA • Messenger RNA • Ribosomal RNA • Transfer RNA • Transcription • RNA polymerase • Promoter • Intron • Exon

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