Transcript History of DNA

Scientists and their
contributions to the
theory of the DNA
molecule
The following scientists contributed to
the theory of the DNA molecule:
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Friedrich Miescher
Phoebus Levene
Frederick Griffith
Joachim Hammerling
Avery, MacLeod and McCarty
Erwin Chargaff
Hershey et Chase
Wilkins and Franklin
James Watson et Francis Crick
Crick and co-workers
Friedrich Miescher
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1869 - Swiss scientist Friedrich
Miescher was the first person to
isolate the material in the
nucleus that had an acid nature.
He called it nucleic acid.
Phoebus Levene
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1920's – P.A. Levene determined
that nucleic acid contained
deoxyribose sugar, a phosphate
group, and 4 nitrogenous bases.
He didn’t know the exact molecular
arrangement, but he did know that
one sugar, one phosphate and one
nitrogenous base linked together to
form a unit (he called this unit a
nucleotide).
Frederick Griffith
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1928 - Frederick Griffith was
trying to find a vaccine for
pneumonia when he found that
“something” transformed the
harmless bacteria into the
harmful bacteria. It was later
determined that this “something”
was DNA.
Joachim Hammerling
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1930s – Joachim Hammerling
hypothesized that hereditary
information is stored in the nucleus.
He experimented with green algae
and observed that regeneration of
new appendages was driven by the
nucleus-containing “foot” of the alga.
Avery, MacLeod, et McCarty
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1944 - Avery, MacLeod, et
McCarty identified DNA as the
transforming material in Griffith’s
experiment on bacteria.
Erwin Chargaff
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1951- Chargaff determined that
the amount of adenine equalled
the amount of thymine and the
amount of guanine equalled the
amount of cytosine.
This is known as the « Rule of
Chargaff »
Hershey et Chase
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1952 - Al Hershey & Martha
Chase used viruses which
attack bacteria (bacteriophages)
to show that it is only the DNA
from the phage that enters the
bacteria and takes control, not
the entire phage.
Wilkins and Franklin
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1953 - Maurice Wilkins and
Rosalind Franklin (both
radiologists) gave Watson &
Crick the most important
information that helped them
solve the DNA riddle -> X-ray
data that showed the repeating
units of DNA formed a double
helix.
James Watson and Francis Crick
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1953- Watson and
Crick determined
the double helix
arrangement of
DNA (Cambridge,
England)
The DNA double
helix model was
intorduced to the
world in the
magazine Nature
in 1953.
Francis Crick and Co-workers
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1961 - Francis Crick &
coworkers discovered the triplet
codon that codes for an amino
acid during protein synthesis.
DNA molecule