Structure of dna
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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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Structure of dna

Structure of DNA


Do now

Do Now

  • Read and React

  • 10 minutes to Read and React with 10 lines


Homework

Homework

  • Define (Page 362-365)

    • RNA

    • Messenger RNA

    • Ribosomal RNA

    • Transfer RNA

    • Transcription

    • RNA polymerase

    • Promoter

    • Intron

    • Exon


Review homework

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


Review homework1

Review Homework

  • What was the experimental variable that Avery used when he repeated Griffith’s work?

    • Molecule-destroying enzyme he used


Review homework2

Review Homework

  • What conclusions did Hershey and Chase draw from their experiments?

    • DNA is the genetic material found in genes


Components of dna

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


Components of dna1

Components of DNA

  • Nitrogen bases are bases that contain nitrogen

  • These bases stick out sideways from each other

  • Can be joined in any order


Structure of dna1

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


Structure of dna2

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


The double helix

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


The double helix1

The Double Helix

  • Like a twisted ladder or a spiral staircase

  • Each strand is “antiparallel”

    • Antiparallel?

    • Run in opposite directions


Base pairing

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


Final questions

Final Questions

  • Why did scientists have to resort to methods other than a microscope?

  • Explain the idea of base pairing?


Homework1

Homework

  • Define (Page 362-365)

    • RNA

    • Messenger RNA

    • Ribosomal RNA

    • Transfer RNA

    • Transcription

    • RNA polymerase

    • Promoter

    • Intron

    • Exon


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