What defines the paradigm of

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What defines the paradigm of molecular biology?
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Central Dogma of Molecular Biology
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Who discovered DNA?
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Historical Events

• 1869 Friedrich Miescher identified DNA, which he
  called nuclein, from pus cells
• 1889 Richard Altman renamed nuclein nucleic acid
• 1928 Griffith discovered that genetic information
  could be passed from one
• bacteria to another known as the transforming
  principle
• 1944 Avery showed that the transforming material
  was pure DNA not protein,
• lipid or carbohydrate.
• 1952 Hershey and Chase used bacteriophage
  (virus) and E. coli to show that only
• viral DNA entered the host
• 1953 Watson and Crick discovered the structure
  of DNA was a double helix

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Historical Events

• 1869 Friedrich Miescher identified DNA, which he
  called nuclein, from pus cells
• 1889 Richard Altman renamed nuclein nucleic acid
• 1928 Griffith discovered that genetic information
  could be passed from one
• bacteria to another known as the transforming
  principle
• 1944 Avery showed that the transforming material
  was pure DNA not protein,
• lipid or carbohydrate.
• 1952 Hershey and Chase used bacteriophage
  (virus) and E. coli to show that only
• viral DNA entered the host
• 1953 Watson and Crick discovered the structure
  of DNA was a double helix

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Historical Events

• 1869 Friedrich Miescher identified DNA, which he
  called nuclein, from pus cells
• 1889 Richard Altman renamed nuclein nucleic acid
• 1928 Griffith discovered that genetic information
  could be passed from one
• bacteria to another known as the transforming
  principle
• 1944 Avery showed that the transforming material
  was pure DNA not protein,
• lipid or carbohydrate.
• 1952 Hershey and Chase used bacteriophage
  (virus) and E. coli to show that only
• viral DNA entered the host
• 1953 Watson and Crick discovered the structure
  of DNA was a double helix

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Nucleoside
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Composition of Nucleic Acid
Purines
Pyrimidines
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B DNA Z DNA                                  
                     
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A, B, AND Z-DNA's                               
                                    
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bases sugar phosphate
1. Large hole in center 2. Sugar phosphate
backbone is at the edge 3. Bases are
displaced towards edge
1. Bases in center (no hole) 2. Phosphates at
periphery
1. Bases present throughout the matrix of the
helix 2. No exclusive domains for either
bases or backbone
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(TFO)
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Bent DNA occurs in AT tracts
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anticlockwise
clockwise
Becomes untwisted
overwinds
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Hybridization
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Hybridization
1. DNA DNA (least stable) 2. RNA - RNA
(intramolecular pairing) 3. DNA - RNA - most
stable (intermolecular pairing)
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DNA Melting
Tm melting temp. at which half of DNA is ss and
half ds Tm 85-90oC
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Effects of Salt Concentration on DNA Stability
Salt increases stability by interfering with
the negative charges of the phosphates.
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Chromosome