History of The discovery of DNA
Johann Friedrich Mieschner
1869
Mieschner discovered
large molecules in the
nucleus of the cell that
were acidic .
He called them nucleic
acids.
He didn’t know what they
were for.
Frederick Griffith
1928
• 80 years later
• Bacteria could share “genetic
material”.
• It could transfer from 1
bacteria to another
Griffith’s Experiment
Frederick Griffith’s experiment
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There were 2 kinds of Pneumonococcus bacteria
Rough strain was harmless to the mice.
Smooth strain killed the mice.
If he heat killed the smooth strain then the mice
lived.
• If he mixed the heat killed smooth bacteria with
the rough strain, then the mice died.
• Something was transferred from the dead
bacteria into the live innocuous bacteria that
made it deadly. .
Oswald Avery and coworkers Colin
McCleod and Maclyn McCarty
1944
• Common belief was protein
carried the genetic
information.
• Avery removed all the
protein from the bacteria
and repeated the Griffith
experiment. It still
transformed the Bacteria
• DNA was the “something”
that carried the genetic
information
Linus Pauling
1950
• Protein chains were helical.
The first twist is called the
alpha helix.
• The 2nd twist is the beta
sheets
• DNA was similar also helical.
• He won 2 Nobel prizes 1 in
chemistry for protein
structure.
• Nobel peace prize for his
work vs. above ground
nuclear testing.
Rosalind Franklin
1951
• She perfected the
technique of x-ray
chrystalography
• Took the first photographs
of DNA
• Identified 2 kinds
• Her unpublished papers
inspired and supported
Watson and Crick.
• Personality clashes with
her collegue Wilkins,
prevented her from
getting credit.
Erwin Chargaff
1951
• 2 rules
• Using paper
chromatography he
found the amount of
adenine = thiame
• And the amount of
cytosine = guanine
• Different species had
different ratios of
nitrogen bases.
James Watson and Francis Crick
1953
• Discovered the double helix
structure of DNA.
• Twisted ladder (Left handed
twist)
• Sugar phosphates sides (anti
parallel)
• Nitrogen bases for rungs
(Complimentary)
• As you can see they stood on
the support of their collegues.
• Won the Nobel Prize 1962 with
Maurice Wilkins. Rosalind
Franklin was not included
Matthew Messelson and
Franklin W. Stahl
1958 • Determined the
method by which
DNA replicated.
• If it was the “Stuff
of inhertance” it
had to duplicate.
• One new strand
and one old strand
(Semi conservative)
Crick and coworkers
1961
• The triplicate code
• Three DNA nucleotides code for 1 amino acid
Nirenberg and coworkers
1964
• Supported Crick’s hypothesis
Human Genome Project
2003
• identify all the approximately 20,00025,000 genes in human DNA,
• determine the sequences of the 3
billion chemical base pairs that make
up human DNA,
• 1993 NIH & Dept of Energy joined to
become the National Human
Genome Research Institute (NHGRI)
Headed by Francis Collins.
• 1998 Craig Venter and Celera
Genomics wanted to do it privately
and get patents for the genes.
• This was deemed unethical in 2000
but the competition speeded up the
process