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

2. 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.

3. 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.

4. 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.

5. 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.

6. 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:

7. 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