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    1st hour 1st hour Presentation Transcript

    • CHAPTER 4: Expression Of Biological Information (6 Hours)
    • CHAPTER 4: EXPRESSION OF BIOLOGICAL INFORMATION
      • 4.1 DNA and Genetic
      • Information (2 hrs)
      • 4.2 DNA Replication (2 hrs)
      • 4.3 Protein Synthesis (1½ hrs)
      • 4.4 Lactose Operon (30 mins)
    • 4.1 DNA & Genetic Information
      • 4.1.1 DNA structure –
      • Watson and Crick Model
      • 4.1.2 DNA– as the carrier of
      • genetic information
      • 4.1.3 Gene concept; one gene
      • one polypeptide
    • 4.1: DNA Structure- Watson & Crick Model
      • DNA is a double-stranded polymer.
      • Each DNA molecule has 2 bonding:-
      • Phosphodiester linkage
      • - has strong covalent bond.
      • 2) Hydrogen bonding
      • - maintained the helix shape
      • - linked the 2 nitrogenous bases
      • Nucleic Acid
        • DNA
        • RNA
      • Each nucleotide consists of:1 phosphate group
        • 1 pentose sugar
        • 1 organic/nitrogenous base
      • 2 types of pentose sugar :
            • Ribose : RNA
            • Deoxyribose : DNA
      DNA Structure
      • There are 4 types of organic bases for DNA:-
      • Purines
      • ( double ringed structure )
      • A denine (A)
      • G uanine (G)
      • 2. Pyrimidine
      • ( two single ringed structure )
      • C ytosine (C)
      • T hymine (T)
      Adenine = Thymine Guanine = Cytosine
    • DNA structure – Watson & Crick Model (Nobel Laureate)
      • Consist of 2 polynucleotide chains.
      • Anti-parallel (opposite direction).
      • Both chain are linked to the other by pairs of organic bases which are themselves joined by hydrogen bonds.
    • Nucleotide Basic Structure O CH 2 Base O P OH O OH OH 1 2 3’ 4 5’
      • Phosphate group
      • Pentose Sugar (5C)
      • Organic Bases
    • DNA DNA molecule structure 5` phosphodiester linkage Hydrogen bond o P o P o P o P P o P o P o P o C T G A A T G C 5` 3` 3` Hydrogen bond
    • BASIC STRUCTURE OF DNA
    • BASIC STRUCTURE OF DNA
    • IF……. So…
    • DNA as the carrier of genetic information
      • Characteristic that are required of genetic material, can be able to:
      • store information
      • replicate, in order to be in each cell of growing organism
      • control expression of traits
      • Encode the sequence of proteins
      • Change in a controlled away, in order to ensure survival of a species in a changing environment
      • There are experiments that were conducted to prove that DNA is the genetic material.
      • Griffith Experiment (1931)
      • Hereditary Information Can Pass between Organisms
      • Avery, MacLeod & McCarty Experiment (Avery et . al .(1944))
      • Find out that the transforming agent is the DNA
      • Beadle and Tatum Experiment (1941)
      •  Gene Concept : One gene One polypeptide
      • The Griffith Experiment
      • Discovery of Transformation  
        • Griffith injected mice with various strains of bacteria
        • Streptococcus pneumoniae ( known as pneumococcus)
          • Virulent, coated bacteria (Smooth form) lethal to mice  
          • Non-virulent, coatless strain (Rough form) not lethal  
          • Coat necessary for infection  
    • Wild type S mooth, virulent ( IIIS ) Mutant type R ough, non-virulent ( IIR ) Symbol of bacteria
      • TRANSFORMATION
      • (1931 F. GRIFFITH)
      • Observation :
      • Conclusion:
      • Living R cells are converted to S cells
      • Transformation occurred
      • Question:
      • Was the “ transforming agent ” protein or DNA, or what?
      Controls Living S (smooth) cells + mouse = mouse dead Living R (rough) cells + mouse = mouse healthy Heat-killed S cells + mouse = mouse healthy Combinations Heat-killed S cells + Living R cells + mouse = mouse dead
      • prove that the transforming principle is DNA - Use purified DNA from types S (smooth) and was treated with: * DNase : break down DNA * RNase : degrades RNA * Protease : degrades protein
      The Avery et. al. Experiment
    • Experiments carried out by Avery et. al.
    • Conclusion:
      • The “transforming agent” was in fact DNA