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Discovery of Nucleic Acids
Friedrich Miescher isolated the genetic material from white blood cell nuclei. He called it NUCLEIN. -
Period: to
Frederick Griffith
He studied two strains of Streptococcus that cause pneumonia, and he was the first person that discover the bacterial transformation.
In 1928 he reported the first widely accepted demostrations of bacterial transformation. -
Discovery of DNA components
Phoebus Levene discovered all the components of DNA:
- adenine
- guanine
- thymine
- cytosine
- deoxyribose phosphate
He also defined phosphate-sugar-base units called NUCLEOTIDES. -
Levene's Tetranucleotide
Levene considered that there were four nucleotides per molecule.
He came to a conclusion, which was that DNA could not store the genetic code because it was chemically too simple. -
Avery, McLeod and McCarty
They determined what actually caused the transformation, and they figured this out by taking the live rough and the heat-treated S, just exactly the same as Griffith had done, but they mixed them with one of two enzymes. One group was mixed with a protease (a protease destroy protein), the other was mixed with a DNase which destroy DNA. -
Journal of Experimental Medicine
This big discovery. It was published in February, and here they suggest that DNA, rather that protein, may be the hereditary material of bacteria - and perhaps in higher organisms as well. -
Double Elix?
Watson and Crick wrote a paper in which they described DNA as a double helix with sugars and phosphates at the center and the nucleobases facing the outside. This model was quickly shown to be incorrect and in fact it made no chemical sense. Although it is only usually attributed to the aforementioned scientists, Rosalin Franklin had an equal or more important role than them. -
Counting Nucleobases
Erwin Charwaff
Used paper chromatography and UV spectroscopy to examine the abundance of the nucleobases and he started to notice something very odd.
In addition, based on the knowledge provided by him, there is now the method of "Counting Nucleobases". -
Hershey-Chase Experiments
They both confirmed DNA as the genetic material, which had been proposed in 1944 in the experiment of Avery, MacLeod and McCarty.
They did the experiment with the "T2 phage", a type of bacterium that affects enterobacteria such as Escherichia Coli. -
Photo 51
This was the photography they observed Franklin and her alongside doctorate student Raymond Gosling who was under her supervision.
Now is a very famous phto that shows the DNA. -
The Nobel Prize in Physiology or Medicine
In this nobel prize award ceremony, the nobel could not be given to rosalind franklin because she died earlier due to x-ray exposure, but it could be given to:
- James Watson
- Francis Crick
- Maurice Wilkins