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This was discovered by: Friedrich Miescher. He was a Swiss physician biologist. Isolated the genetic material from white blood cell nuclei. He noted it had an acidic nature and called it nuclein -
What did the duo actually discover? Many people believe that American biologist James Watson and English physicist Francis Crick discovered DNA in the 1950s. In reality, this is not the case. Rather, DNA was first identified in the late 1860s by Swiss chemist Friedrich Miescher. Determined the components of DNA:
- Adenine, guanine, thymine, cytosine, deoxyribose phosphate. Defined phosphate-sugar-base units called nucleotides -
Levene is known for his tetranucleotide hypothesis which proposed that DNA was made up of equal amounts of adenine, guanine, cytosine, and thymine. Before the later work of Erwin Chargaff, it was widely thought that DNA was organized into repeating tetranucleotides in a way that could not carry genetic information. Levene proposed that there were four nucleotides per molecule. DNA could not store the genetic code because is was chemically far too simple -
FREDERICK GRIFFITH
Studied the epidemiology and patology of 2 strains of Streptococus pneumoniae. What is Bacterial Transformation? Bacterial transformation is a process of horizontal gene transfer by which some bacteria take up foreign genetic material (naked DNA) from the environment. It was first reported in Streptococcus pneumoniae by Griffith in 1928. Griffth used two strains of Streptococus:
- TYPE S: virulent (deadly)
- TYPE R: non-virulent (harmless) -
he rule that in DNA there is always equality in quantity between the bases A and T and between the bases G and C. (A is adenine, T is thymine, G is guanine, and C is cytosine.) Named for the great Austrian-American biochemist Erwin Chargaff (1905-2002) at Columbia University who discovered this rule. -
The paper suggested that DNA, rather than protein, may be the hereditary material of bacteria- and perhaps in higher organism as well. -
Determined the cause of the transformation in Griffith's Experiment. They took live R and Heat-Treated S and mixed it with one of two enzimes:
- PROTEASES: which destroys protein.
- DNase: which destroys DNA. -
Watson and Crick wrote a paper which they described DNA as 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. -
Used a paper chromatography and UV spectroscopy to examine the abundance of the nucleobases and he started to notice something very odd... -
In 1951 and 1952, Alfred Hershey and Martha Chase conducted a series of experiments at the Carnegie Institute of Washington in Cold Spring Harbo. Used phages and radiolabeled phosphorus and sulfur
Hershey and Chase concluded that DNA, not protein, was the genetic material. A protective protein coat was formed around the bacteriophage, but the internal DNA is what conferred its ability to produce progeny inside bacteria. -
The discovery in 1953 of the double helix, the twisted-ladder structure of deoxyribonucleic acid (DNA), by James Watson and Francis Crick marked a milestone in the history of science and gave rise to modern molecular biology.- The backbone is made of sugar (deoxyribose) and phosphate groups.
- Hydrogen bonds between the nucleobases : A-T & G-C.
- The sequence of nucleobases codifies the amino acid sequence of a protein.
- Strings of base pairs that code for a product are called genes.
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The Nobel Prize in Physiology or Medicine 1962 was awarded jointly to Francis Harry Compton Crick, James Dewey Watson and Maurice Hugh Frederick Wilkins "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material"