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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#