DNA StructureImagine you are an arc

DNA Structure
Imagine you are an architect or engineer. You have been commissioned to build a house. What is the first thing you need to do before you even order the building materials? You will need to work on the blueprints of the building. These let you know where and what to build.

Whether it is a set of blueprints to be used in the construction of a building, or a recipe for cooking spaghetti , a proper set of instructions is crucial for success. The blueprints of every organism are found in its DNA. Every cell in the same organism contains the same set of DNA. Every species has a unique set of instructions that make it different from another closely related species.

Any model of the DNA molecule must be able to explain how it stores all the information needed to control the activities of the cell as well as how the information is passed on to subsequent generations.

The Race to Unravel the DNA Structure
by the early 1950s, Nobel prize-winning chemist Linus Pauling from the USA had worked out thehelical structure common to many fibrous proteins. Since evidence indicated that DNA was also a fibrous molecule, he then attempted to derive the structure of DNA based on that model.

In London, Maurice Wilkins and Rosalind Franklin of King’s College were tackling the same problem using the technique of X-ray crystallography. This involved passing X-ray through pure fibers of the salt of DNA in order to obtain complex X-ray diffraction patterns. From these patterns, the gross structure of the molecule could be derived.

A third approach by James Watson and Francis Crick of the Cavendish Laboratory in Cambridge which ultimately reveled the DNA structure involved building a model of the DNA molecule that incorporated information they could gather.
Two lines of evidence proved crucial .Firstly, both Watson and Crick had access to the X-ray diffraction data of Wilkin and Franklin. Secondly , they realised the significance of the evidence published by Erwin Chagaff in 1951 concerning the ratio of the different nucleotide bases known to be present in DNA
From the X-ray diffraction photographs, Watson and crick deduced that there were two helices present in DNA .from Chargaff’s data, they realized that the bases of DNA were always present in fixed pairs . that is, adenine paired with thymine, and guanine paired with cytosine.


Their final model of the DNA molecule consisted of two chains of polynucleotides, with each chain in from of a helical spiral (see figure 3.10) Hydrogen bonds present between the pairs of bases of neighboring chains caused the chains to coil around each other, forming a double helix


As Watson and crick noted in the announcement of their finding in 1953,”… the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.”

Sine that momentous unveiling of the structure of DNA more than fifty year ago, progress in understanding the mysteries of heredity and developmental biology has been phenomenal. In 2003, the genetic code of men, the blueprint of life was unraveled. Hopefully, this will lead to a revolution in Man’s ability to detect, treat and prevent disease.