Biology

Only available on StudyMode
  • Download(s) : 90
  • Published : October 13, 2012
Open Document
Text Preview
Discuss the chain of events that led to the discovery of DNA as the heritable substance and the discovery of the structure of DNA.

Ans> The chain of events led to the discovery of DNA as the heritable substance and the discovery of the structure of DNA. In the late nineteenth century, a German biochemist Friedrich Miescher found the nucleic acids which are long-chain polymers of nucleotides, and are made up of sugar, phosphoric acid, and several nitrogen-containing bases. Later it was found that the sugar in nucleic acid can be ribose or deoxyribose, giving two formsie RNA and DNA. In 1943, American Oswald Avery proved that DNA carries genetic information. He even suggested DNA might actually be the gene. Usually people thought that the gene would be protein, not nucleic acid, but by the late 1940s, DNA was largely accepted as the genetic molecule.

In 1948, Linus Pauling discovered that many proteins take the shape of an alpha helix, spiraled like a spring coil. In 1950, Erwin Chargaff found that the arrangement of nitrogen bases in DNA varied widely, but the amount of certain bases always occurred in a one-to-one ratio. In the early 1950s, there was a race to discover DNA among scientists. At Cambridge University, Francis Crick along with James Watson showed a great interest and were impressed by Pauling's work. Meanwhile in London, Maurice Wilkins and Rosalind Franklin were also studying DNA. The Cambridge team's approach was to make physical models to narrow down the possibilities and eventually create an accurate picture of the molecule. The london team took an experimental approach, looking particularly at x-ray diffraction images of DNA. In 1951, Watson attended a lecture by Franklin. She had found that DNA can exist in two forms, depending on the relative humidity in the surrounding air which helped her deduce that the phosphate part of the molecule was on the outside. Watson and crick based on this information, made a failed model. It caused...
tracking img