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Miescher and the discovery of the nucleic acid
Johan Friedrich Miescher,in 1846, isolated the nuclein, a mix of nucleic acids and protein, from the nuclei of some white cells that he took from the pus of surgical wounds, using an alkaline solution. he found the nuclein in every cell type he tested. -
Levene identified the components of DNA
Poebus Levene , in the nearly 1900s, identified the components of DNA: deoxyribose and the ribose.He also discovered that DNA molecules were made of a string of a nucleotide units linked togheter by a phosphate group. Levene thouth that the chain was composed of 4 nucleotides: adenine, thymine, cytosine and guanine, and this hypotesys is called tetranucleotide hypotesis. He also thought that DNA molucles didn't carry genetic informations. despite these discoveries, his conception was wrong -
Avery: the DNA is the inheritance molecule
Oswald Avery and his co-workers discovered that DNA is the material of wich chromosomes and genes are made of. DNA was recognised as the molecule resposible for passing genetic characteristics. -
Chargaff finds out the different amount of nitrogenous bases
Erwin Chargaff isolated DNA from different organism and measured the levels of each of the four nitrogenous bases.He found out that the amount of thymine is very close to the amount of adenine, and there's just as much in guanine as there's cytosine. Chargaff, so, said that the tetranucleotide hypotesis wasn't correct, beause, if this theory was correct, the amounts of A,T,G and C would be the same in all DNA of all organism, and this is not correct. -
Rosalind Franklin discover helical structure of the DNA
Rosalind Franklin was a biophysicist and a X-ray crystallographer, who made a huge discovery: she demonstrated the helical structure of the DNA, providing an X-ray diffraction image of DNA, wich leads, after two years, to the discovery of the DNA double helix structure by Watson and Crick -
Watson and Crick: the model of the double helix of DNA
On the base of Franklin's studies, James Watson and Francis Crick, built thei model of the double helyx of DNA, and on the base of the Chargaff's studies, they discovered that adenine always hydrogen bonds with thymine, and guanine always hydrogen bonds with citosine.
