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Discovery of Nucleic Acids
Nucleic acids were discovered in 1868, when Friedrich Miescher isolated a new compound from the nuclei of white blood cells.
Nucleic acids are large biomolecules that play essential roles in all cells and viruses. A major function of nucleic acids involves the storage and expression of genomic information. DNA encodes the information cells need to make proteins. -
Levene's Tetranucleotide
The tetranucleotide hypothesis of Phoebus Levene proposed that DNA was composed of repeating sequences of four nucleotides. It was very influential for three decades, and was developed by Levene. -
Griffith transformation experiment
The “Griffith's Experiment,” conducted in 1928 by English bacteriologist Frederick Griffith described the conversion of a non-pathogenic pneumococcal bacteria to a virulent strain. In this experiment, Griffith mixed the living non-virulent bacteria with a heat inactivated virulent form. -
Avery, MacLeod and McCarty
In 1944, they explained Frederick Griffith's results. They determined what actually caused the transformations.
They figured this out by taking the live rough, and
they heat-treated S, but they mixed them with 1 or 2 enzymes.
One group was mixed with a protease (destroys protein).
The other was mixed with a DNase which destroys DNA. This showed that it was the DNA that was responsible for the transformation. -
Journal of experimental medicine
The discovery was published in February 1944, and they suggested that it is DNA and not protein that may be the hereditary material of bacteria. -
Counting Nucleobases
Erwin Chargaff discovered that DNA is the primary constituent of the gene, thereby helping to create a new approach to the study of the biology of heredity. -
Hershey-Chase Experiments
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 -
So, it's the DNA
The race was on to determine the structure of DNA in cells and to determine how it codes for proteins and how it replicates
The problem: DNA exists in two forms
A form (dry form)
B form (wet form, as DNA exists in cells) -
Doble helix
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 -
Eureka
James Watson and Francis Crick, 1953
Basically, when Rosalind Franklin takes photo 51, he sends it to his king's college London. The same, makes it to reach James Watson and Francis Crick who, thanks to the photo, just discover the entire structure of DNA and end up being credited with the discovery. -
Triple Helix
Linus Pauling and Robert Corey proposed a triple helix structure for DNA -
The nobel prize in Physiology or medicine
The Nobel Prize in Physiology or Medicine in 1962 was awarded to James Watson, Francis Crick and Maurice Wilkins for their discovery of the molecular structure of DNA, which helped solve one of the most important of all biological riddles. For the discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material. -
DNA is a double-standed helix
The backbone is made of sugar (deoxyribose) and phosphate groups
Hydrogen bonds between the nucleobases: A-T and 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.