the discovery of
DNA
Gregor
Mendel
Gregor Mendel estimated the existence of a
hereditary molecule that passes genetic
information through generations. Through
experimenting with "true-breeding" pea plants,
he noticed an important pattern. When a
yellow pea plant and a green pea plant were
bred together their offspring was always yellow.
1866
Frederick
Meishcher
1869
Griffith
1928
oswald Avery, Colin
McLeod
& Maclyn McCarty
1944
Edward
Chargaff
1952
Griffith conducted an experiment with 2 different strain's of
the pneumonia bacteria, the harmful S-strain and harmless
R-strain. He injected these strains in various combinations
into mice to observe the outcome.
This was the first experiment showing that bacteria are
capable of transferring genetic information from nearby
bacteria to use the DNA as its own through a process known
as transformation
The team of 3 conducted similar experiments Through many
biochemical steps, they were able to purify the transforming
principle by washing away, separating out or destroying the
other cellular components ,it was found that the substance
was not a protein, which was what was expected, but rather
a nucleic acid. Today we know that It as DNA
His first theory was the first to hint at the invention of
the DNA, the base pairs. His second theory further
established the fact that DNA was the genetic material,
not proteins. His work was important to future research.
1950
Alfred Hershey &
Martha Chase
Frederick Meishcher was interested in the
composition of the cell nucleus. He hypothesized that
proteins were the hereditary material as they were
known to be complex and carry out various biological
functions.
The chemical composition and function of this newly
discovered molecule were not determined for
another 50 years. What he identified as nuclein is
now identified as DNA.
these two were interested in what was the genetic material in
cells, the protein or DNA. They worked with the bacteria E.
coli and a virus, which infects bacteria, which had both DNA
and a protein coat and injected the virus into the DNA.They
knew that bacteria could be transformed by viruses however
were unaware which part of the virus did this, the protein
coat or DNA.The results were conclusive and indicated that
DNA was responsible for carrying genetic information.
Rosalind Franklin &
The two used X-ray crystallography to study the
Maurice Wilkins
shape of the DNA molecule. Wilkins had produced
1952
a few tests of the DNA crystallography that
suggested its helical structure but the DNA
samples were poorly prepared making the
crystallography's difficult to interpret.
James Watson &
Francis Crick
1952
Gathering all the information other scientists discovered, Watson
and Crick began to build a model of DNA. With everything they had
to incorporate, they realized DNA must be in a double helix
structure. In their model, each strand of the helix was made up of
phosphate and sugar backbone and the nitrogenous bases were
attached to the backbone, directed towards the centre of the
molecule. The two determined that DNA would only be stable if the
strands ran anti parallel and twisted around each other in clockwise
direction. Their model also showed that the nitrogenous bases are
connected by hydrogen bonds, keeping the two strands together.
Matthew these two scientists grew E. coli in a heavy nitrogen
isotope. Matthew and franklin knew how often E. coli cells
Meselson & divided, so they were able to collect small samples in each
generation to extract and purify the DNA. Information
Franklin Stahl from each generation supported the theory that DNA
1958
copy semi-conservatively.the two scientists did their
experiments in E. coli, it led to the understanding that
semi-conservative DNA duplicate is a global tool shared
by all living organisms.