Deoxyribonucleic Acid (DNA)
DNA stands for deoxyribonucleic acid, it is located in the nuclei of cells which make up the body. DNA is quite often referred to as one of the building blocks of the body.. It is made up of four bases known as:
James Watson, Francis Crick, Maurice Wilkins, Rosalind Franklin Crick and Watson, together with Maurice Wilkins, won the 1962 Nobel Prize in physiology or medicine for their 1953 determination of the structure of deoxyribonucleic acid (DNA) this was one of the most significant scientific discoveries of the 20th century. James Watson and Francis Crick discovered the molecular structure of DNA model of the structure resembled a twisted rope ladder. They proposed that the DNA molecule consisted of two spirally wound, helical chains.
Rosalind Franklin (1920–1958)
Franklin had established herself as a world expert in the structure of graphite and other carbon compounds. Rosalind Franklin had discovered that DNA could crystallize into two different forms, an A form and a B form. John Randall (was a physicist who led the King’s College London team which worked on the structure of DNA) gave Franklin the A form and Wilkins the B form, assigning them each the task of elucidating their molecular structure. Wilkins and Franklin used X-ray crystallography as a technique to set out their experiment. The steps to this technique are simple, you just need to expose a crystal to X-ray in order to produce a diffraction pattern. Once you have a pure enough diffraction patterns it is possible to then reconstruct the positioning of the atom within the molecules that make up the basic unit also referred to as the unit cell. DNA is a very complex molecule that’s why it took scientists a long time to learn to do this.
Many impure diffraction patterns were formed during this due to the mix up of the A and B forms of DNA. This made it hard to interpret. Rosalind and Franklin’s discovery of the A and B forms of DNA lead to the development of an ingenious method to separate the two forms. This provided us with the first DNA crystals that were pure enough to produce clear diffraction patterns. She then went on to obtain excellent X-ray diffraction patterns of crystalline B-form DNA and, using a combination of crystallographic theory and chemical reasoning, discovered important basic facts about its structure. She discovered that the sugar-phosphate backbone of DNA lies on the outside of the molecule, not the inside as was previously thought. She discovered the helical structure of DNA has two strands, not three as proposed in competing theories. She gave quantitative details about the shape and size of the double helix.
The all- important missing piece of the puzzle that she could not discover from her data was how the bases paired on the inside of the helix, and thus the secret of heredity itself. That discovery remained for Watson and Crick to make. James Dewey Watson (1928-2004) and Francis Crick (1916 – 2004) The X-ray crystallography experiments of Franklin and Wilkins provided much information about DNA – in particular that DNA was a molecule in which two “strands” formed a tightly linked pair. Watson heard Wilkins talk on the molecular structure of DNA and saw his recent X-ray crystallographic photographs of DNA, he was hooked. Watson then soon moved to the Cavendish Laboratory, where several important X-ray crystallographic projects were already under go.
Working under Perutz was Francis Crick, who had earned a bachelor’s degree in physics from University College London. Crick, another physicist in biology, was supposed to be writing a dissertation on the X-ray crystallography of haemoglobin when Watson arrived, eager to recruit a colleague for work on DNA. Watson and Crick rapidly put together several models of DNA and attempted to incorporate all the evidence they could gather. Franklin’s excellent X-ray photographs were critical to the correct solution although they had been gained access without her permission. The scientists announced the structure of DNA in articles that appeared together in the same issue of Nature. Crick and Watson made the spontaneous leap: in 1953, they proposed that the structure of DNA was a winding helix in which pairs of bases (adenine – thymine and guanine – cytosine) held the two strands together.
The Watson – Crick Model of the DNA double helix provided enormous impetus for research in the emerging fields of molecular genetics and biochemistry, and Crick, Watson, and Wilkins were awarded the Nobel Prize in 1962. Then they moved off in different directions. Watson’s subsequent career lead him to become a director from 1968 onward he led it to new heights as a center of research in molecular biology at Cold Spring Harbor Laboratory (CSHL) of Quantitative Biology on Long Island, New York. Watson has played a significant role in the development of science policy, from the War on Cancer, through the debates over the use of recombinant DNA, to promoting the Human Genome Project.
From 1988 to 1992, he ran the Human Genome Project at the National Institutes of Health while still directing Cold Spring Harbor Laboratory. During Crick’s long tenure at Cambridge, he made also helped and made fundamental contributions to unlocking the genetic code. He then demonstrated that each group of three adjacent bases on a single DNA strand codes for one specific amino acid. He also correctly hypothesized the existence of tRNA, which mediates between mRNA and amino acids.
Human Genome Project
Completed in 2003, the Human Genome Project (HGP) was a 13-year project. The human genome project was an international research effort to sequence and map all of the genes -together known as the genome – of members of our species, Homo sapiens, identifying and mapping the approximately 20,000–25,000 genes.
Aspects of Rosalind Franklins were informally communicated to Watson and Crick by Maurice Wilkins and Max Perutz, without her or John Randall’s knowledge. This shows that crick and Watson clearly depended on Rosalind Franklin results in order to make the next steps in figuring out the DNA structure. Although once they had found the first building block’s they figured out everything else pretty quickly. The co-operation between the scientists is clearly shown throughout the essay as firstly James Watson, Francis Crick, Maurice Wilkins worked hand in hand to collect all the data and work in collaboration in order to find out the DNA sequence.
Without this collaboration the work would have been made harder to do between the scientists as the result wouldn’t not be put together and would be left to chance just as the case with Rosalind Franklin. Secondly the human genome project which was an absolute massive project whereby scientists all over the worked helped and played there bit. The communication between the scientists was vital there because if one scientist had found something his results would be tested and no-more time would be wasted to find the same gene thereby speeding the process.
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