The Structure, Replication, and Repair of DNA

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The Structure, Replication, and Repair of DNA
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Chapter Overview

• The Evidence for DNA as the Genetic Material
• The Chemical Components/Structure of DNA
• The Evolution of the Concept of the Gene
• The Replication of DNA
• The Mutation and Repair of DNA

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What is the Genetic Material?
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Fred Griffith (1928)
Oswald Avery (1930s) tested various components
of heat-killed bacteria for ability to transform
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Bacteriophages-Further Evidence that DNA was the
genetic material

• Bacteriophages are viruses that infect and
  replicate in bacterial cells
• Studies showed that bacteriophages consisted of
  DNA and protein, and that part of the virus did
  not enter the host

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Chase and Hershey
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The Chemical Components/Structure of DNA
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Some Key Clues to Discovering the Structure of DNA

• Rosalind Franklin and Maurice Wilkins
• Chargaffs Rules
• James Watson and Francis Crick

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The Evolution of the Concept of a Gene?
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One Gene-One Enzyme Hypothesis

• Archibold Garrod (1902)- alkaptonuria appeared to
  be an inherited disease

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George Beadle and Edward Tatum (1941)

• Mutants of Neurospora show that several genes
  are required for arginine biosynthesis

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One Gene-One Polypeptide

• Sickle Cell Anemia- a recessive, inherited
  disease
• Linus Pauling showed that hemoglobin was
  defective in patients

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The Replication of DNA
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The Mechanics of DNA Replication
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DNA Replication Requires Enzymes and Specific DNA
Sequence Elements

• Origin of Replication
• DNA Helicase
• DNA Polymerase
• DNA Primase
• DNA Ligase

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The Mutation and Repair of DNA
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What is a mutation?

• Any change in the sequence of a particular DNA
  molecule
• Mutagens are agents that speed up the rate of
  mutation
• How often do mutations occur?

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Categorizing Mutations

• Point Mutations- change in single nucleotide or
  the insertion/deletion of a few nucleotides
• Chromosomal Mutations (translocations,
  inversions, deletions, duplications)

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Repair of Thymine Dimers