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THE DISCOVERY OF DNA • scientists worked for over 100 years before DNA was confirmed to be the hereditary material for all life Late 1869 • Fredrich Miescher isolated nonprotein substance from the nucleus of pus cells • he noted that a phosphorus rich substance was present and it did not behave like a protein (at the time, proteins were thought to be the hereditary material 1920s • Frederick Griffith experimented with mice • he used two strains of mice (virulent/nonvirulent) • coined the term “transformation” – heat did not render the DNA useless and was taken up by living bacteria and incorporated into bacterial genome 1930’s •Joachim Hammerling worked with a one-cell green algae (Acetabularia) Cap – top Stalk – stem Foot - nucleus Concluded that the hereditary material is located in the nucleus 1949 • Erwin Chargaff – discovered that the amount of adenine is equal to the amount of thymine and the amount of cytosine is equal to the amount of guanine 1952 • Alfred Hershey & Martha Chase • infected bacterial cells with radioactively labelled viruses • noted that phosphorus containing DNA transferred to infect bacteria 1953 • Rosalind Frankilin produced an X ray diffraction pattern of DNA that suggested it was in the shape of a double helix 1953 James Watson & Francis Crick deduced the structure using information from the work of Chargaff and Franklin DNA REPLICATION • replication is semiconservative • experimental support for Watson & Crick came from Mattthew Meselson and Franklin Stahl • Meselson & Stahl experiment suggested that each new strand consists of an original parent strand and a newly synthesized strand http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter14/animations.html# DNA REPLICATION http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter14/animations.html#