-
Meischer Isolating DNA
Meischer during 1869 was studying white blood cells to understand the chemistry of the cells. He would take bandages from hospitals, add a saline solution to clean the bandages, then when they are clean the puss would remain. From there he added a weak alkeline solution which made a precipitate form from the cells which was the nucleus. Within each nucleus he was able to isolate a certain chemical which he called Nucelin which was high in phosphorous, as is DNA -
Morgan and Fruit Flies
During Janurary 1910 Thomas Hunt Morgan discovered that certain fruit flies had different eye colours to other fruit flies. Morgan then proceeded to test these flies, he bred the fly with the white eyes with the common red-eye fruit fly. All flies in this generation had red eyes. He then proceeded to breed two red-eyed flies, and there was a white-eyed fly in the generation which was male while the others were red-eyed. This suggested that the red-eye was a dominant gene in the X-Chromosome. -
Chargaff's Rule
Chargaff in 1950 thought there would be more to DNA than repetitive tetrenucleotide blocks. He proceeded to isolate the DNA from different organisms and measured the levels of the nitrogenous molecules. What turned out was that the Adenine and Thymine had similar levels to each other while the Guanine and Cytosine also have similar levels to each other. This disproves the presence of a tetranucleotide block. -
X-Ray Definition.
During 1951 Rosiland Franklin and Maurice Wilkins were using X-ray Diffraction to look at the shapes of different molecules, and they decided to use it on the all too mysterious DNA. What was found was a perculiar shape, which turns out to be an 'X' shape which is the shape of a helix. A different shape was also created (from a different direction) which helped find the dimensions of the DNA which would then help the building of a model of DNA. -
The Double Helix
James Watson and Francis Crick published the first DNA model, which was created by the knowledge of the composition of DNA to determine the structure. The most important part of this is the knowledge of the basic structure which is the Sugar-Phosphate backbone of the DNA with the nitrogenous bonds. They figured out that the nitrogenous bonds would be the same size when the A and T combine, and the C and G combine, which creates the equal width of the Helix. The helix was discovered by Francis. -
Kornberg and the DNA Polymerase
During 1957 Arthur Kornberg was trying to isolate the enzyme that synthesises DNA which is DNA Polymerase. He had extracted DNA Polymerase fron E. Coli which he then added to a salene solution that contained a strand of DNA but also all the parts of DNA but the Thymine was radioactivally tagged. When incubated at body temperature (approx 37*C) the Tymine turned up in a completely different strand of DNA. The DNA Polymerase had recreated the original strand exactly.
