Deoxyribonucleic acid (DNA)

Deoxyribonucleic acid (DNA) is the basic genetic material of most living organisms. Although a large and apparently complex molecule, the structure of DNA is in fact astonishingly simple.

A single DNA molecule consists of two separate strands wound around each other to form a double-helical (spiral) structure. Each strand is made up of a combination of just four chemical components known as nucleotides- all of which have the same basic composition.

Each nucleotide consists of a sugar molecule (deoxyribose) linked to a phosphate group to form the helical backbone; different nucleotides are distinguished only by the identity of the nitrogen-based unit called the nucleotide base bonded to the sugar molecule.
The four bases are:

(A) adenine
(C) cytosine
(G) guanine
(T thymine


The bases lie in the central region of the double helix, with each base linked by hydrogen bonds to specific complementary base on the partner strand.

The base pair rule states that wherever you have an A on one strand, there will be a T at the same relative position on the other strand; wherever you have a G on one strand, you will have a C on the other strand.

In addition, the number of molecules of A in a sample always equals the number of molecules of T. Similarly, the number of C molecules always equals the number of molecules of G.

DNA is therefore basically a linear information macro molecules much like the long strips of computer tape used in the first computers.

A typical DNA base sequence might be:
5'-AGCTTATTGCATAAGCGCGAT-3'
5' and 3' These refer to the left-hand and the right-hand ends respectively of a DNA or RNA base sequence.