Download Evidence for DNA Structure and Function

Evidence for DNA Structure
and Function
TIMELINE OF IMPORTANT EXPERIMENTS
Timeline – Important Discoveries
• Griffith
1928 • Transformation – good cells turned bad
• Avery, McCarty, Macleod
1944 • DNA is the transforming factor
• Chargaff
1950 • A-T and C-G ratios
• Franklin
1951 • X-ray diffraction photos of DNA
• Chase and Hershey
1952 • Radioactive viruses show DNA is hereditary molecule
• Watson and Crick
1953 • Develop 3-D structure of DNA
Evidence for DNA Structure/Function
 Griffith (1928)
 Harmless bacteria
could be
transformed by a
‘factor’ found in
harmful bacteria
Evidence of DNA Structure/Function
 Avery, et al. (1944)
 Repeated Griffith’s
experiment to determine
the transforming ‘factor’
 Using enzymes to
destroy DNA, RNA and
proteins
 Mice survived when
DNA was destroyed
Evidence for DNA Structure/Function
 Chargaff (1950)
 Determined equal ratios
of adenine and thymine
in any given DNA
sample
 Determined equal ratios
of cytosine and guanine
in any given DNA
sample
Evidence for DNA Structure/Function
 Franklin (1951)
 Used X-ray
diffraction through
crystallized DNA
 Indicated spiral
structure
 Consistent diameter
and cross-connectors
Evidence for DNA Structure/Function
 Hershey and Chase (1952)
 Bacteriophage virus – protein coat
labeled with radioactive sulfur; DNA
with radioactive phosphorus
 After infection, separate bacteria
from virus and look for radioactivity
 If S-35 is with bacteria = protein has
caused transformation
 If P-32 is with bacteria = DNA has
caused transformation
Evidence for DNA Structure/Function
 Hershey and Chase (1954)
 P-32 with bacteria confirms DNA as the ‘factor’
Evidence for DNA Structure/Function
 Watson and Crick
(1953)
 Used evidence from
Franklin, Chargaff and
others to determine
detailed chemistry of
DNA