The Structure of DNA Rachel Cooke, Heidi Kenneally, Emily Harper

Who Discovered DNA? There are four people responsible for the discovery of the common double-helix structure of DNA. They were called Francis Crick, James Watson, Maurice Wilkins and Rosalind Franklin.

Maurice Wilkins and Rosalind Franklin Maurice Wilkins and Rosalind Franklin were the first people to obtain very good x-ray diffraction images of DNA fibres. Though these photos did not show the structure of DNA, there were patterns on those images that could be used to determine the position of the DNA molecule’s atoms. From these images, Franklin determined that the DNA molecule must be long and thin.

James Watson and Francis Crick In 1951 James Watson and Francis Crick began to examine the DNA’s structure. Using previous X-ray diffraction photos of DNA fibers taken by Wilkins and Franklin, they discovered that it showed an X shape, which is also the characteristics of a helix. In April of 1953, using this information, they came up with the double helix, the structure that is almost always associated with DNA.

The Basic Structure of DNA The double helix is formed from two identical strands that complement each other perfectly. Four nucleotides are chemically joined together A, T, C, G, through sugar and phosphate molecules in the backbone. A base pairs with T and C base pairs with G.

DNA The building block of DNA is made up of Nucleotides. The general structure is shown below:-   p Phosphate Group O base CH2 o Deoxyribose is a 5 Carbon sugar (Pentose). Its molecular structure is the same as Ribose apart from Deoxyribose has one less Oxygen atom in its molecule. (See below) 5 Carbon sugar Ribose: Deoxyribose:

The Nucleotides are joined to the next by covalent bonds between their sugars and phosphates.   The organic bases A+T and C+G can also be called “Complimentary bases pairing” because they fit together exactly:- A T G C = Hydrogen bonds