Biology (Chapter 14)

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Biology (Chapter 14)
2012-10-11 11:17:55

Biology Notes
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  1. James Watson and Francis Crick 
    Used modeling to determine that DNA was helical, and contain two polypeptide chains that run anti paralell in the molecule
  2. Maurice Wilkins 
    English biophysicist that prepared uniform samples of DNA fiber, superior to any previously made
  3. Rosalind Franklin
    Performed X-Ray Crystollography on a strand of DNA, which helped characterize DNA
  4. Hershey and Chase 
  5. Meselson and Stahl
    Devised a simple experiment to distinguish old strands of DNA from new ones and hence proved that DNA replication is semiconservative
  6. Erwin Chargaff
    Discovered regularities in DNA; Adenine=Thymine and Cytosine=Guanine
  7. Complementary Base Pairing
    Copying mechanism for the genetic material; each single strand of DN could serve as a guide to produce a new double stranded molecule identical to the original
  8. Purine
    • Double carbon ring structures
    • Adenine and Guanine
  9. Pyrimidine
    • Single carbon ring structures
    • Cytosine and Thymine 
  10. DNA Replication
    • DNA is a template for the reaction
    • DNA with and enzyme and 4 precursors (Nitrogen base and sugar, but no phosphate) can replicate itself in a test tube.
  11. Semiconservative Method of DNA Replication
    Produces two copies that each contained one of the original strands and one new strand
  12. Helicase 
    Enzymes unwind the double helix in DNA replication, using ATP energy
  13. DNA Polymerase
    An enzyme used in DNA replication
  14. RNA Primer/RNA Primase
    An RNA primer is a short single strand of RNA, this RNA complementary to the DNA template strand is formed by an enzyme-RNA primase 
  15. Ligase 
    An enzyme that catalyzes the joining of Okazaki fragments to form one continuous DNA lagging strand
  16. Leading Strand
    The template strand of the DNA double helix so that the replication fork moves along it in the 3' to 5' direction
  17. Lagging Strand
    Strand that is being built from the replcation fork 5' to 3', but has to wait for a nitrogen base to be exposed
  18. Okazaki Fragment
    Newly synthesized stretches of lagging strand DNA
  19. Repair Mechanisms
    • Mechanisms that fix DNA strands that have flaws 
    • Proofreading- removes improper nucleotide and retries
    • Mismatch Pair- detects "wrong" bases
  20. Excision Repair
    If DNA becomes damaged during the life of the cell, certain enzymes "inspect" the cell's DNA
  21. Replication Fork
    Moving Y shaped structures tha tare the regions where new DNA strands are being synthesized 
  22. Prokaryote Genome
    Helicases act at a specific point on the DNA, which is circular; this point is called an origin of replication.
  23. Eukaryote Genome
    DNA is linear but replication does not begin at the ends of the molecules; each eukaryotic chromosome has many origins of replication
  24. Telomeres
    A region of repetitive nucleotide sequences at each end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes
  25. Telomerase
    A ribonucleoprotein that is an enzyme which adds DNA sequence repeats ("TTAGGG" in all vertebrates) to the 3' end of DNA strands in the telomereregions, which are found at the ends of eukaryotic chromosomes
  26. Photorepair
    ...Blast a cell with UV light so that 99 per cent of the cell, including its DNA, is destroyed, you can almost entirely repair the damage in a single day just by illuminating the cell with the same wavelength at a much weaker intensity.