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Discovery of Nucleic Acids
Friendrich Miescher (1844-1895), a physicist and biologist, discovered genetic material by isolating nucleic acid from the nuclei of white blood cells. He concluded that it was acidic in nature and called it nuclein. -
Discovery of DNA components
Phoebus Levene , an American biochemist of Lithuanian origin, discovered the components of DNA, and discovered that its components consisted of: adenine, guanine, thymine, cytosine, deoxyribose, phospate, deoxyribose, and phospate.1869-1940
defined phosphate-sugar-base units called nucleotides -
Levene's Tetranucleoide
Levene,Thought that the structure of the molecules was a tetranucleotide structure. He said that there were four nocleotides per molecul, and that this made a simple sructure that it couldn't possibily bethe key to unlocking heredity. But he war wrong because DNA could not store the genetic code for the reason that was chemically far too simple. -
Griffithi's Transformation Experiment
For his experiment, he used two strains of streptococcus:
- Type S: virulent (deadly)
streptococcus pneumoniae:
S is for (smoothe colonies) Kill the mice
R is for (Rough colonies) do not kill the mice
If you inject the smothe colonies strain in to the mose, they kill the mouse but if they use the Rought colonies the mice didn't die. But then if you use head-killed smoth strain the mice is alive and then if ypu mixed rough strain and head killed smooth strain the mice die. -
Frederick Griffith
Frederick Griffith (1879.1941) a british bacteriologist. He investigated the epidemiology and pathology of 2 strains of streptococcus pneumoniae
He was the first person who actually demostrate bacterial transformation -
Avery,MacLeod and McCarty
The answer the question of how this the transformation experiment of griffiths works.
They figure this out by taking the live rought and heat-treated S just excally the same as griffith did before and mixed it with one of two enzymes. one was mixed with proteases ( destroyes protein)
the other one DNase (destroyes DNA)
They get the conclusion that the DNA was the responsible of the transformation. -
Journal of Experimental Medicine
the article explains that dna may be the hereditary material of bacteria, not protein, and perhaps also of higher organisms. -
Double Helix DNA
Watson and Crick wrote a paper which they described DNA as a double helix. -
Counting Nucleobases
There was someone who starts counting nucleobesas, he was Erwin chargaff (1905-2002) an austrian biochemist. For that he used paper chromatography and UV spectroscopy, then he started to notice something very strange.all the alive things get the same result. -
Hershey and Chase
The bacteriophage is a virus that infects bacteria. For the experiment they used a bacteria cell, then they took bacteriophages, so then they used radioactive DNA to follow the moviment of DNA during the infecction. The result was no radioactive bacterias inside the pallet. -
Triple helix DNA
Linus Pauling and Robert Corey proposed a triple helix structure for DNA -
Conclusions of Hersheys and chase
Hershey and Chase concluded that the genetic matrix was DNA without protein. What has happened is that a protective protein coat has formed on the outside of the bacteriophage, but the internal DNA is what gave it its ability to produce progeny inside the bacteria.
so in conclusion it's the dna. -
Photo 51 by Rosalind Frankling
Rosalind TOOk this picture of X-ray direction Image of DNA this is called photo 51 by Rosalind Frankling. This photo shows clearly the x in the middle that is a sing of a double helix.