DNA stands for deoxyribonucleic acid and is used in the body to carry and transfer information that influences the physical and behavioral characteristics of an organism. DNA consists of two unbranched polynucleotide chains made of 4 types of nucleotide. Each nucleotide is made of three parts; a nitrogen containing organic base, a pentose sugar and one or more phosphate groups. The organic base is one of four types but they all contain nitrogen; adenine (A), guanine (G), cytosine (C) and thymine (T). The nucleotides in each polynucleotide chain are joined together between the phosphate group of one nucleotide and the hydroxyl group on carbon 3 of the sugar on another nucleotide. The two-polynucleotide chains of each DNA molecule are joined by pairs of bases held together by hydrogen bonds. These bonds are individually quite weak but in large numbers very strong. This helps to make DNA a very stable molecule which is an essential feature for a molecule, which carries and transfers vital information. .
The fact that the polypeptides are joined together only by hydrogen bonds means that they can easily be broken and the strands can separate for replication and protein synthesis which allows for information to be transferred. DNA is a large molecule therefore it can store large amounts of information, this is essential as the organisms entire genetic code and instructions for life in a sense need to be stored in a secure molecule which easily allows for replication. Guanine will always pair with cytosine by means of three hydrogen bonds. Adenine will always pair with thymine by the means of 2 hydrogen bonds. Base pairing allows for the protection of genetic information from being corrupted by external chemical and physical processes, which protects the genetic information and therefore information can be transferred without being damaged. DNA has a universal code which means that there are the same triplet of bases which code for an amino acid in all organisms, for example UUU codes for Pheline in all organisms.