DNA Synthesis - DNA Synthesis Ch. 16 pp. 305-319

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DNA Synthesis Ch. 16 pp. 305-319 “If you think our society is intrinsically bad, there is no doubt in my mind that the double helix will enable it to be worse than you can possibly fear. If on the other hand you are like me, and you are optimistic, you will think that the knowledge that it will provide will give sufficient improvement in human welfare to ensure that the good outweighs the bad.” R. J. Gosling (1995) in D.N.A. Genesis of a Discovery. He was a student with Rosalind Franklin when they made the first X-ray diffraction studies of DNA. DNA structure with metal cutouts of base structure made by Watson and Crick (Science Museum, London UK)
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DNA synthesis I: Four classic experiments on DNA ( genetic material and replication). DNA synthesis II: The biochemistry of DNA replication. The problems and solutions. DNA synthesis III: Mutation, its origin, consequences and repair.
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I. Four classic experiments on DNA as the genetic material A. The transforming factor is genetic information . (1920) Frederick Griffith found that Streptococcus bacterial cells can be “transformed” from non-virulent (benign) to virulent cells.
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Recall: Is the coat the cell wall?
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Polysaccharide coat
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S Virulent + Benign ` S R R Infect mouse Dead and leaky Live Are S or R cells recovered ? R R R R Two experiments:
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B. What is the molecular composition of the transforming factor? 1944 O. Avery, C. McLeod and M. McCarty At the time proteins were known to have enormous information potential. And DNA seemed to be “dull” in comparison.
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TF No enzyme + R cells Protease + R cells RNase + R cells DNase + R cells S cells S cells S cells R cells Amylase + R cells S cells Their experiments and results: What can they conclude?
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C. Molecular-genetic proof that genes are found in DNA, not protein Alfred Hershey (MSU alumnus and Nobel laureate) and Martha Chase used a bacteriophage (bacterial virus) of only a protein coat surrounding a DNA genome
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T2 bacteriophage attaches to E. coli and then 20 minutes later the cell lyses releases 200 newly formed T2. What could be used to radioactively label DNA but not protein and protein but not DNA?
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DNA Synthesis - DNA Synthesis Ch. 16 pp. 305-319

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