Essay on The Discovery Of The Structure Of DNA

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James Watson and Francis Crick discovered the structure of DNA, but only by drawing on the work of many scientists who came before them. (Maddox, 2003) In 1944, Oswald T. Avery, Colin M. MacLeod, and Maclyn McCarty published “Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types”, which was the first scientific work to identify DNA as the molecule that carried genetic information, and became a breakthrough at that time. (Avery, Macleod, & McCarty, 1944) Before Avery and coworkers published their paper, there was very little interest in DNA among scientists in the field of genetics. Very little was known about DNA, however, early analyses suggested that it was a very simple molecule, at least in…show more content…
Griffith worked with two strains of the bacteria pneumococcus, named according to the appearance the colonies grown from each strain. The S-strain possessed a polysaccharide coat and formed large, smooth colonies. The R-strain did not have a polysaccharide covering, and grew in small, rough colonies. In addition to influencing colony appearance, the polysaccharide shell also protected the S-strain from the host immune response. Griffith noticed that mice injected with the S-strain eventually became ill and died, while mice injected with the R-strain suffered no ill effects. He also noted that S-strain pneumococci that had been killed by heat caused no harm. But Griffith’s breakthrough came when he found that mice injected with a mixture of live R-strain and heat-killed S-strain died from infection. Furthermore, he was able to isolate live S-strain bacteria from these dead mice. From this, Griffith was able to conclude that the heat-killed cells contained a “transforming code” capable of changing the harmless R-strain bacteria into the pathogenic S-strain. Francis Crick and James Watson are recognized as the main scientists involved in the identification of DNA and its structure, which is one of the most important discoveries of the twentieth century. However, were it not for Rosalind Franklin, Linus Pauling, Colin Avery and Maurice Wilkins, the two men would likely not have made
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