The History of DNA structure slide show

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The History of DNA structure : 

The History of DNA structure Wikimedia Commons http://en.wikipedia.org/wiki/File:DNA_orbit_animated_static_thumb.png

The History of the Equipment and Background Discoveries that helped in the discovery of DNA structure : 

The History of the Equipment and Background Discoveries that helped in the discovery of DNA structure

Antonie Van Leeuwenhoek : 

Antonie Van Leeuwenhoek Helped create the first microscope Discovered the nucleus examining red blood cells in salmon Other scientist also a credited with the discovery of the nucleus (Franz Bauer in 1804 and Robert Brown in 1831). Image of Antonie Van Leeuwenhoek reuslts on examinations of Salmon red blood cells. From: Wikimedia Commons http://en.wikipedia.org/wiki/File:Leeuwenhoek1719RedBloodCells.jpg

Karl Wilhelm von Nägeli : 

Karl Wilhelm von Nägeli The discovery of chromosomes in 1842 Used a new die of basophilic aniline was also important for the discovery of DNA. From : Wikimedia Commons http://en.wikipedia.org/wiki/File:Carl_Wilhelm_von_Naegeli.jpg

Mendal’s Law of Inhertiance : 

Mendal’s Law of Inhertiance The idea that there was some unit of inheritance started in 1856 with Mendal’s experiments with pea plants. Unfortunately through lack of equipment, Mendal could not take his research to the next level. Summary of Mendal’s results. From Wikimedia Commons http://en.wikipedia.org/wiki/File:Mendel_seven_characters.svg

Walther Flemming : 

Walther Flemming The discovery of mitosis and cell division in 1870 Important as it hinted that the nucleus and chromosomes might be somehow be linked to inheritance as all cells replicate by this process. Walther Flemming research material. From: Wikimedia Commons http://en.wikipedia.org/wiki/File:Flemming1882Tafel1Fig14.jpg

The True Search for a Unit of Inheritance Only Truly Started in the 20 Century With the Rediscovery of Mendel’s Experiments and Ongoing Improvements in Scientific Equipment : 

The True Search for a Unit of Inheritance Only Truly Started in the 20 Century With the Rediscovery of Mendel’s Experiments and Ongoing Improvements in Scientific Equipment

Walter Sutton and Theodor Boveri : 

Walter Sutton and Theodor Boveri 1919 Both linked chromosomes and Mendel’s theory of inheritance independently from each other. Walter Sutton was in Columbia University Theodor Boveri in Germany. This discovery sparked the interest in studying genes and the race to discover how inheritance worked began. (Walter Sutton on the left and Theodor Boveri on the right) From: Wikimedia Commons http://en.wikipedia.org/wiki/File:Theodor_boveri_walter_sutton.png

Phoebus Levene : 

Phoebus Levene In 1919 he discovered that DNA was composted of a base (adenine, cytosine, guanine and thymine), sugar unit and phosphate (i.e. the nucleotide). He was also able to identify RNA and separate it from DNA. : GNU Free Documentation License http://en.wikipedia.org/wiki/File:Tetranucleotide_.png

First Attempt at the Structure of DNA : 

First Attempt at the Structure of DNA 1935 Erwin Schroedinger, (one of the fathers of quantum mechanics) and Max Delbruck, (and a student of Niels Bohr at the time). A gene “a quantum mechanical system that derived its stability from the height of the energy barrier separating one state from another”. Genes formed “a periodic crystal or solid”, and that this accounted for how genes did not change radically over time. Their theory failed, but their example inspired others to try and gave them a base to work from.

William Astbury : 

William Astbury Invented X-ray diffraction patterns showing structure of DNA Wikimedia Commons http://commons.wikimedia.org/wiki/File:Xray_DNA.gif

George Beadle and Edward Tatum : 

George Beadle and Edward Tatum 1943 the one gene = one enzyme/protein. Neurospora crassa was mutated using x-rays. Some enzyme to changed.

Avery, MacLeod and McCarty : 

Avery, MacLeod and McCarty In 1944, search for what makes up DNA Used Fred Griffith information on pneumonia’s two strains in 1928. Smooth (S) {deadly form, as the immune system does not recognise coating on the bacteria that cause pneumonia} and rough (R) {less deadly, as there is no coating to prevent an immune response}.

Fred Griffith Pneumonia : 

Fred Griffith Pneumonia 1928, two forms Smooth (S) {deadly form, as the immune system does not recognise coating on the bacteria that cause pneumonia} Rough (R) {less deadly, as there is no coating to prevent an immune response}. GNU Free Documentation License http://en.wikipedia.org/wiki/File:Tetranucleotide_.png

Slide 15: 

In the experiment the smooth strain was killed, by heating, and mixed with the rough strain, than the host was killed. DNA transforming as this was the only way that the rough strain could kill if the gene for the smooth strains coating was transferred to it. DNA was the carrier of biological specificity in bacteria. Wikimedia Commons (showing DNA transference) http://en.wikipedia.org/wiki/File:Griffith_experiment.svg

Alexander Todd : 

Alexander Todd In 1951 he discovered the chemical bonds that link the nucleotides in DNA.

Erwin Chargaff : 

Erwin Chargaff In 1951 created a new technique for paper chromatography that allowed him to measure the amount of bases (adenine, cytosine, guanine and thymine) in DNA. Noticed that the amount of adenine and thymine was the same, and the amount of cytosine and guanine was the same. “Chargaff’s rule states that DNA from any cell of all organism should have a 1:1 ratio of pyrimidine and purine bases and, more specifically, that the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine”.

Linus Pauling : 

Linus Pauling 1951 hypothesized that protein folds into an a-helix complex. Used his own knowledge of how chemicals interact with each other. Conformed by Sir Lawrence Bragg(inventor of X-ray crystallography) who saw this arrangement when he X-rayed proteins Max Pereitz when he made synthetic polypeptides that formed an a-helix.

Hershey-Chase experiment : 

Hershey-Chase experiment In 1952, genes are made of DNA became accepted conclusively A bacteria and a phage 1) Sulphur (necessary for protein synthesis) was replaced with a radioactive substance to make the protein. In a centrifuge the left over phage that did not enter the bacteria and the bacteria were separated, the protein was in the liquid portion only. 2) DNA was made radioactive to label. After the centrifuge the pellet part was labelled. Protein from the phage did not enter the bacteria, but DNA did Caused geneticists to concentrate on DNA and its properties. Wikimedia Commons (showing DNA transference) http://en.wikipedia.org/wiki/File:Griffith_experiment.svg

James D. Watson and Francis Crick First Attempt at the Structure of DNA : 

James D. Watson and Francis Crick First Attempt at the Structure of DNA 1952, they collected the results of other scientist also trying to work out the structure of DNA a helix, but the model had the backbone of DNA in the centre of the DNA complex. Upon consolation with Rosalind Franklin and Rayond Gosling, (working with X-ray diffractions of DNA) The model was disregarded as being wrong when compared to the pictures of DNA from X-ray diffractions.

Linus Paulings DNA Structure : 

Linus Paulings DNA Structure 1953 the model had three intertwined backbones that formed a dense centre. Paulings thought that the phosphate component was attached by hydrogen bonding, this type of bonding was supposed stabilize the negative charge of DNA. When this model was test however, very acidic conditions that were not found in the cell were necessary for this structure to form.

The Correct Solution by Watson and Crick : 

The Correct Solution by Watson and Crick Inspired by Paulings model Discovery of an X-ray diffraction of a so called B form of DNA (they were using the A form for the first model) from Rosalind Franklin Bases where on the inside and phosphate-sugar complex on the outside. Watson and Crick also came up with how the bases hydrogen bond with each other. Wikimedia Commons http://en.wikipedia.org/wiki/File:DNA_Model_Crick-Watson.jpg

In Conclusion : 

In Conclusion The structure of DNA was a big break through in the scientific community and this discovery can not just be accredited to one person or one group, but was a joint effect by various people in a wide range of scientific fields

This has been brought to you by group one in BMOL20010 from Stage two Science in UCD.By Zara Bolger : 

This has been brought to you by group one in BMOL20010 from Stage two Science in UCD.By Zara Bolger

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