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1st hour


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1st hour

  1. 1. CHAPTER 4: Expression Of Biological Information (6 Hours)
  2. 2. CHAPTER 4: EXPRESSION OF BIOLOGICAL INFORMATION <ul><li>4.1 DNA and Genetic </li></ul><ul><li>Information (2 hrs) </li></ul><ul><li>4.2 DNA Replication (2 hrs) </li></ul><ul><li>4.3 Protein Synthesis (1½ hrs) </li></ul><ul><li>4.4 Lactose Operon (30 mins) </li></ul>
  3. 3. 4.1 DNA & Genetic Information <ul><li>4.1.1 DNA structure – </li></ul><ul><li>Watson and Crick Model </li></ul><ul><li>4.1.2 DNA– as the carrier of </li></ul><ul><li>genetic information </li></ul><ul><li>4.1.3 Gene concept; one gene </li></ul><ul><li>one polypeptide </li></ul>
  4. 4. 4.1: DNA Structure- Watson & Crick Model <ul><li>DNA is a double-stranded polymer. </li></ul><ul><li>Each DNA molecule has 2 bonding:- </li></ul><ul><li>Phosphodiester linkage </li></ul><ul><li>- has strong covalent bond. </li></ul><ul><li>2) Hydrogen bonding </li></ul><ul><li>- maintained the helix shape </li></ul><ul><li>- linked the 2 nitrogenous bases </li></ul>
  5. 5. <ul><li>Nucleic Acid </li></ul><ul><ul><li>DNA </li></ul></ul><ul><ul><li>RNA </li></ul></ul><ul><li>Each nucleotide consists of:1 phosphate group </li></ul><ul><ul><li>1 pentose sugar </li></ul></ul><ul><ul><li>1 organic/nitrogenous base </li></ul></ul><ul><li>2 types of pentose sugar : </li></ul><ul><ul><ul><ul><li>Ribose : RNA </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Deoxyribose : DNA </li></ul></ul></ul></ul>DNA Structure
  6. 6. <ul><li>There are 4 types of organic bases for DNA:- </li></ul><ul><li>Purines </li></ul><ul><li>( double ringed structure ) </li></ul><ul><li>A denine (A) </li></ul><ul><li>G uanine (G) </li></ul><ul><li>2. Pyrimidine </li></ul><ul><li>( two single ringed structure ) </li></ul><ul><li>C ytosine (C) </li></ul><ul><li>T hymine (T) </li></ul>Adenine = Thymine Guanine = Cytosine
  7. 7. DNA structure – Watson & Crick Model (Nobel Laureate) <ul><li>Consist of 2 polynucleotide chains. </li></ul><ul><li>Anti-parallel (opposite direction). </li></ul><ul><li>Both chain are linked to the other by pairs of organic bases which are themselves joined by hydrogen bonds. </li></ul>
  8. 8. Nucleotide Basic Structure O CH 2 Base O P OH O OH OH 1 2 3’ 4 5’ <ul><li>Phosphate group </li></ul><ul><li>Pentose Sugar (5C) </li></ul><ul><li>Organic Bases </li></ul>
  9. 9. 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
  12. 12. IF……. So…
  13. 13. DNA as the carrier of genetic information <ul><li>Characteristic that are required of genetic material, can be able to: </li></ul><ul><li>store information </li></ul><ul><li>replicate, in order to be in each cell of growing organism </li></ul><ul><li>control expression of traits </li></ul><ul><li>Encode the sequence of proteins </li></ul><ul><li>Change in a controlled away, in order to ensure survival of a species in a changing environment </li></ul>
  14. 14. <ul><li>There are experiments that were conducted to prove that DNA is the genetic material. </li></ul><ul><li>Griffith Experiment (1931) </li></ul><ul><li>Hereditary Information Can Pass between Organisms </li></ul><ul><li>Avery, MacLeod & McCarty Experiment (Avery et . al .(1944)) </li></ul><ul><li>Find out that the transforming agent is the DNA </li></ul><ul><li>Beadle and Tatum Experiment (1941) </li></ul><ul><li> Gene Concept : One gene One polypeptide </li></ul>
  15. 15. <ul><li>The Griffith Experiment </li></ul><ul><li>Discovery of Transformation   </li></ul><ul><ul><li>Griffith injected mice with various strains of bacteria </li></ul></ul><ul><ul><li>Streptococcus pneumoniae ( known as pneumococcus) </li></ul></ul><ul><ul><ul><li>Virulent, coated bacteria (Smooth form) lethal to mice   </li></ul></ul></ul><ul><ul><ul><li>Non-virulent, coatless strain (Rough form) not lethal   </li></ul></ul></ul><ul><ul><ul><li>Coat necessary for infection   </li></ul></ul></ul>
  16. 16. Wild type S mooth, virulent ( IIIS ) Mutant type R ough, non-virulent ( IIR ) Symbol of bacteria
  17. 17. <ul><li>TRANSFORMATION </li></ul><ul><li>(1931 F. GRIFFITH) </li></ul>
  18. 18. <ul><li>Observation : </li></ul><ul><li>Conclusion: </li></ul><ul><li>Living R cells are converted to S cells </li></ul><ul><li>Transformation occurred </li></ul><ul><li>Question: </li></ul><ul><li>Was the “ transforming agent ” protein or DNA, or what? </li></ul>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
  19. 19. <ul><li>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 </li></ul>The Avery et. al. Experiment
  20. 20. Experiments carried out by Avery et. al.
  21. 21. Conclusion: <ul><li>The “transforming agent” was in fact DNA </li></ul>