-
DISCOVERY OF THE NUCLEIC ACIDS
Friedrich Miescher (siwss physician and biologist) isolated the genetic material from white blood cells nuclei. He detected an acid nature -
DISCOVERY OF DNA COMPONENTS
Phoebus Levene (lithuan-american biochemist) the discoverer of the components and who determined thet they where: adenine, guanine, thymine, cytosine, deoxyribose phosphate and defined-phosphate-sugar-base units called nucleotides. -
THEORY OF THE TETRANUCLEOTIDE
Phoebus Loven proposed that there were four nucleotides per moluecule. This theory was weong sine the genetic code was too simple to be stored inside. -
BACTERIAL TRANSFORMATION
Frederick Griffith (british bacteriologist) he reported and demostrated a bacterial transformation -
GRIFFITH'S EXPERIMENT
He used two strains of streptococcus: type S (smooth) which is virulent and type R (rought) non virulent. they did the following experiment using mices as a test: strain r injected: mouse lives, strain s injected: the mouse dies, heat killed s strain: mouse lives and heat killed strain s mixed with r strain: mouse dies. This shows a transformation but in that time Griffith did not discover why. -
DISCOVERY
The why of the mutation was discovered by 3 people, Oswald Avery (canadian physician), Colin MacLeod (canadian-american geneticist) and Maclyn McCarty (american geneticist) -
AVERY'S, MACLEOD'S AND MCCARTY'S EXPERIMENT
To determine this they made the same experiment as Griffith, but in one of the test strands they added proteases (wich destroys protein) and in the other they added DNase (wich destroys DNA). The one mixed with protease killed the mouse but the one with Dnase didn't kill it, this meant that the DNA was responsible for the transformation. This study was published in the Journal of Wxoerimental Medicine and the article suggested that the DNA was who carried the hereitary material of the bacteria -
DOUBLE HELIX
Watson and Crick wrote a paper in wich they stated and descrived the DNA as a double helix with sugars and phosphates in the center and the nucleobases facing outside. This was quickly descarted since it made no chemichal sense -
COUTING NUCLEOBASES
Erwin Chargaff (austrian biochemist) He was a Columbia proffesor of biochemistry and he was really interested in the abundance of the nucleobases. When investigating those he found something really interesting. The levels of A (adenine) and the levels of T (thymine) where really close or the same and the levels of C (cytosine) and G (Guanine) also really similars. This pattern was repidet in every species. This became the Chargaff's rule wich he didn't realize how important it was. -
HERSHEY-CHASE EXPERIMENTS (II)
The first experiment done with this method they let some phges infect a bacteria, when the phage de-engaged they dicovered that no kind of protein infected the bacteria. But when this was tried with a phage with tadioactivity in the DNA they did find radioactivity in the cell. This concluded with the hipotesis that the genetic material was on the DNA. -
HERSEY-CHASE EXPERIMENTS
Alfred Hershey (american geneticist and biologist) and Martha Chase (american geneticist) they used bacteriophage (phage) wich is a virus that infects bacteriall cells, it's mainly made of DNA and protein. The method they used was the following one: they used a bacterial cell as a host and added a phage with radioactive sulphur wich allowed to follow the movement of the DNA. They allowed the phage to infect the cell and then would separate the main "flesh" of the cell by centrifugatening it. -
TRIPLE HELIX
Limus Pauling (american biochemist) and Robert Coroy (american biochemist) proposed a triple helix structure for the DNA. This theory emerge probably because of the mix of both types A (dry form) and B (wet form as DNA exists) form, obviously this theory was proven wrong. -
PHOTO 51
Rosalind Franklin (british biophisicist) was an excepcional woman who was silenced during decades. She was who took the photo wich was the key for the big discovery of the century, the photo 51 of her colection of x-rays of DNA. This photo was stolen by her boss Maurice Wilkins (new zeland physicist) who sent the photo to James watson (american geneticist) and Francis Crick (american geneticist). This two man knew exactly what was that and instantly made a model based on Rosalind's photo. -
THE 3 ATRICLES
In this exact day 3 diferent articles about the same theory where launched in the same science magazine, Nature. The first article was from Waston and Cricked, the second one was from Stokes and Willson and the last one was from Rosalind and her assistent Gosling -
NOBEL PRIZE
The nobel prize in medicine or physiology was given to Crick, Watson and Wilkins, Rosalin was excluded beacause sadly she died from radiation in 1958 and nobel prizes are not given to dead people. But even though that she never got the recognitzion she deserved from anyone else