Evidence as the Genetic Material

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Evidence as the Genetic Material
2012-11-12 16:58:59

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  1. a.      __ discovered the double- helical model for DNA
    b.      Nucleic acids are unique in their ability to__
                                                                  i.      Hereditary info is encoded in the __and __in all the cells of your body
    • Watson and Crick
    • direct their own replication from monomers
    • chemical language of DNA
    • reproduced

  2. a.      Searching for the Genetic Material
                                                                  i.      __ showed that genes exist as parts of chromosomes
    1.      What was the general belief?

    Disproved through study of bacteria and viruses that infect them
    • T.H. Morgan
    • proteins, due to great heterogeneity and specificity of function, were hereditary material; nucleic acids too uniform

  3.                                                               i.      Discovery of the genetic role of DNA when attempt to develop a vaccine against __ carried out by __
    • pneumonia (streptococcus
    • pneumonia)
    • Frederick Griffith
  4. Explain the Griffith experiment.
    • a.      Had two strains: one pathogenic, one harmless
    • b.      Living S cells injected: dead mouse
    • c.       Living R cells injected: living mouse
    • d.      Dead S cells: living mouse
    • e.       Mixture of dead S cells and living R cells: dead mouse
    •                                                                                                                                       i.      Some living cells became pathogenic through transformation (a change in the genotype and phenotype due to the assimilation of external DNA by a cell)
    •                                                                                                                                     ii.      Pathogenicity trait inherited by all descendants
  5. Explain Oswald Avery's experiment.
    • a.      Wanted to identify transforming substance
    •                                                                                                                                       i.      DNA, RNA, protein
    •                                                                                                                                     ii.      Broke open heat-killed pathogenic bacteria and extracted cell contents, inactivating each molecule, and testing ability to transform 
    • 1.      Only DNA= Avery, MacLeod, McCarthy discovered transforming agent was DNA
  6. Explain Hershey and Chase's experiment
    • a.      Used phages because viruses are much simpler cells with DNA and a protein coat
    • b.      Used T2 ( infects E. coli and turns it into a T2-producing factory
    • c.       Used radioactive sulfur to tag protein and radioactive phosphorus to tag DNA in separate batches
    •                                                                                                                                       i.      Found that phage DNA entered the host cells  but the phage protein did not
    • 1.      Also, when returned to a culture medium, the infection ran its course, and E. coli released phages that contained some radioactive phosphorus, showing DNA played a part of the infection process

  7. 1.      __
    a.       Analyzed base composition of DNA and reported that base composition of DNA __from one species to the next and analyzed ratios of bases
                                                                                                                                          i.      Adenine amounts are equal to __ amounts/ cytosine amounts are equal to __ amounts
    1.      Led to __:
    a.     what are they?
    • Erwin Chargaff
    • varies
    • thymine
    • guanine
    • Chargoff’s rules:
    • 1) base composition varies between species

    • 2) Within a species, the number of A and T bases are equal, and the number of C and G bases are equal