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Discovery of Nucleic Acids
Discovered in 1869 by Friedrich Miescher.
Isolated the genetic material from white blood cell nuclei. He noted it had an acidic nature and called it nuclein -
Phoebus Leven
In 1910, Phoebus Leven determined all components of nucleic acids. Also defined the phosphate and sugar base as nucleotide IMP: this is structure of nucleic acid. -
Frederick Griffith and Griffith transformation experiment
In 1928, Frederick Griffith demonstrated the bacterial transformation.
In this experiment, studied the epidemiology and pathology of two strains of Streptococcus Pneumoniae, this types are the next:
- Type S: virulent (deadly)
- Type R: non-virulent (harmless) -
Experiment Avery–MacLeod–McCarty
In 1944, they showed that chopped up DNA would not cause any harm.
IMP: non-protein DNA may be the hereditary material of bacteria and possibly higher life forms. -
Double Helix (Incorrect theory)
In 1951, 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. -
Erwin Chargaff's theory
Erwin Chargaff was Counting Nucleobases in 1952
Used paper chromatography and UV spectroscopy to examine the abundance of the nucleobases, and he started to notice something very curious.
Amounts of Adenine = Amounts of Thymine
Amounts of Cytosine = Amounts of Guanine
This happened in all spices.
This came to be known as "Chargaff's rules". -
Rosalind Frenklin and Photo 51
Rosalind Franklin photographed her fifty-first X-ray diffraction pattern of deoxyribonucleic acid, or DNA. Photograph 51, or Photo 51, revealed information about DNA´s three-dimensional structure by displaying the way a beam of X-rays scattered off a pure fiber of DNA. -
Hershey and Chase experiment
Hershey and Chase were able to separate the phages into radioactive sulfur-containing protein ghosts and radioactive phosphorus-containing DNA. They found that the radioactive sulfur protein ghosts could attach to bacterial membranes, while the radioactive phosphorus DNA could not.
Hershey and Chase concluded that protein was not genetic material, and that DNA was genetic material. -
Pauling's theory of Triple Helix
To Pauling the strands appeared cylindrical. He guessed, then, that DNA was likely to be a helix. No other conformation would fit both Astbury's x-ray patterns of the molecule and the photos he was seeing.
This is a failed attempt to predict the structure of DNA. The problem with his triple helix model is that the phosphates form the helical core, with the bases pointing outwards. This would be impossible under normal cellular conditions. -
Watson and Crick Corrct Doble Helix
In 1953, Watson and Crick's model, the two strands of the DNA double helix are held together by hydrogen bonds between nitrogenous bases on opposite strands. Each pair of bases lies flat, forming a "rung" on the ladder of the DNA molecule. Base pairs aren't made up of just any combination of bases. -
Nobel prize and Rosalind Franklin
She contributed to a groundbreaking discovery in genetics that would forever be remembered in the history of science – but without her name attached. In her short lifetime of only 37 years, Rosalind Franklin produced research that led to a Nobel Prize, yet she was not one of the awardees