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Discovery of nucleic acids
Friedrich Miescher discover the nucleic acids, isolated the genetic matirial from white blood cell nuclei. -
Discover of DNA components (1869-1940)
Phoevus Levene discover the components of the DNA, sugar pentose, is a sugar that have 5 carbones, phosphate, nitrógenos base. -
Levene's Tetranucleotide
Levene said it was organized by tetrads that there were 4 nucleotides per molecule, and that it was such a simple structure that it was impossible that it was the key to discovering the erence, he was wrong. -
Griffith's Transformation Experiment
In his experiment he used 2 types of streptococci, one of type S which is smooth and forms a capsule that makes the bacteria virulent and deadly, and the type R which is harmless.
He saw that when injecting the R-type strain into a mouse, the reton lived, when injecting the S-type the mouse died, if he injected the S-type but died by heat the mouse lived, but if he injected the R-type with the type S died by heat the reton died, there was a transformation. -
Avery, McLeod and McCarty
Explein the explain the result of Griffith's experiment, they determined what caused the change, they repeat the experiment a one group inject the R-tipe with the S-tipe but dead from heat and the mouses dies, the other group injects the same but mixed with DNAm the mouses lives.
They descover thet the DNA is the responseble of the chenge, came to the conclusion that DNA and not the protein that could be the material ederitaruium of bacteria -
The first model of DNA Watson and Crick
Watson and Crick created the first model, it was a set of two propellers with sugars and di-phosphates in the center and nucleobasses facing outwards. -
Counting Nucleobases
Erwin Chargaff he began to count the bases of the nucleotides in different organisms, and no matter which organism he looked at, he always found the same results, that Adenine and Thymine had a similar amount, Cytosine and Guanine tremble. -
Hershey and Chase
What they did was use a bacterial cell, then they took two types of phage, radioactive sulfur or radioactive DNA, they allowed them to infect the bacteria and then separate them.
What they saw was that the radioactive sulfur phages had created radioactivity on the surface of the bacteria, whereas the radioactive DNA phage had created radioactivity inside the bacteria.
This is how they concluded that the genetic material was DNA and not protein. -
Second model of DNA Linus Pauling
He described the structure of the helices, he devised a triple helix model with the phosphates and the sugar inside and the snucleobases on the outside, taking as a reference some images in X-ray. -
Image of DNA Rosalind Franklin
Rosalin Frnkilin was an X-ray photographer who took many photos of the inside of a cell, the most famous of which is where you can see the x of a DNA double helix, -
Final model of DNA Watson and Crick
They obtained photo 51 of Rosalind Franklin and they managed to make a model of what DNA is like. -
DNA
Nowadays we know that DNA is made up of two helices with a bestebral column made up of groups of sugar and phosphates that function in antipararelo. Hydrogen bonds between the nucleobases, A-T and G-C, that explains why they are always in the same amounts.
