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DNA – THE CODE OF LIFE

DNA – THE CODE OF LIFE. I. The discovery of DNA. A. Friedrich Miescher – extracted DNA from the nucleus of white blood cells. B. Griffith’s Bacterial Transformation (1928) This is an experiment used disease causing and harmless bacteria that were injected into mice.

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DNA – THE CODE OF LIFE

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  1. DNA – THE CODE OF LIFE

  2. I. The discovery of DNA A. Friedrich Miescher – extracted DNA from the nucleus of white blood cells.

  3. B. Griffith’s Bacterial Transformation (1928) • This is an experiment used disease causing and harmless bacteria that were injected into mice. • Griffith wanted to find out if the harmless bacteria can become harmful. • Observations: Harmless bacteria can become harmful if they are mixed with dead harmful bacteria. The harmful characteristic was inherited from one generation to the next.

  4. http://www.youtube.com/watch?v=vQOdDGM5vSg Conclusion: Some chemical component in bacteria act as a transforming factor that cause a heritable change. Bacterial transformation: When bacteria pick up DNA from the environment or other bacteria to use it for their own benefit.

  5. C. The Hershey and Chase Experiment (1952) This experiment used bacteria and viruses (bacteriophage) that only infect bacteria They also used radioactive isotopes to label proteins (radioactive sulfur) and DNA (radioactive phosphorous). These radioactive isotopes were moved into two groups of viruses. They wanted to find out if proteins or DNA are responsible for inheritance. Virus inserts its DNA into bacteria: http://www.youtube.com/watch?v=9hzUjx_oD8E&feature=related

  6. Conclusion: Bacteriophages inject DNA into the host cell, while proteins remain outside. So DNA must be responsible for determining inheritance. http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/bio21.swf::Hershey%20and%20Chase%20Experiment http://www.dnaftb.org/15/ -- animation on all scientists

  7. D. Watson and Crick They were the scientists who proposed a model to describe the structure of DNA They also predicted how DNA doubles itself.

  8. II. The Structure of DNA (Review) • Deoxyribonucleic acid (DNA) is a macromolecule that is built up of nucleotide monomers. • The nucleotide contains: • Deoxyribose • Phosphate • Nitrogen-containing base (A, T, C, G) • Two long polynucleotide chains face each other by their complementary base pairs.

  9. The two long chains are antiparallel to each other and are held together by hydrogen bonds. Base pairing rule: A binds with T; C binds with G

  10. Adenine and guanine are called purine bases because they are made up of two rings. Cytosine and thymine are pyrimidine bases because they are made up of one ring. 1 purine base binds with a pyrimidine base with hydrogen bonds.

  11. The nucleotides bind together by covalent bonds to form the sugar-phosphate backbone of the polynucleotide chain. http://www.pbslearningmedia.org/resource/biot11.sci.life.gen.structureofdna/the-structure-of-dna/

  12. III. DNA REPLICATION • Replication – the process in which one DNA molecule produces two identical DNA molecules • This process is semiconservative – one chain of the DNA molecule is parental while the other half is a new chain. • The parental chain is called a template while the new chain is the complementary chain.

  13. The steps of DNA replication: • DNA unwinds and the hydrogen bonds are separated • The new chain will be built next to the separated old chain by DNA polymerase enzyme. (This enzyme cannot read in the 5’3’ direction and cannot start assembling a chain) • An other enzyme will mark the DNA molecule by inserting RNA nucleotides in a 3’ – 5’ direction so the DNA polymerase enzyme can match up the missing nucleotide and build the leading strand

  14. 4. The replication continues until the entire DNA segment is copied. 5. A different DNA polymerase replaces the RNA primer with DNA nucleotides. 6. The lagging strand is the other side of the DNA molecule that grows away from the replication fork in smaller chunks (discontinuously) 7. First RNA primase marks the beginning of a section, than DNA polymerase begins to synthesize the new section

  15. 8. The DNA needs to unwind more before a new lagging strand piece can be built – Okazaki fragments – discontinuous segments of the lagging strand of the DNA molecule. 9. An other DNA polymerase changes the RNA primers to DNA and ligase attaches the separate fragments to each other. 10. The two new DNA molecules are exact copies of the original DNA. If any mistakes occurred in the copying, new enzymes will correct those. • http://www.wiley.com/college/pratt/0471393878/student/animations/dna_replication/index.html -- more detailed • http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html -- many things on DNA replication and the experiments • http://www.dnalc.org/resources/3d/03-mechanism-of-replication-basic.html

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