DNA

What is DNA
The initials DNA stand for Deoxyribonucleic acid, and it refers to a molecule which carries most of the genetic information used in the reproduction, functioning and development of living organisms and certain viruses.
Composition
As the name suggests, this molecule comprises of a nucleic acid, along with carbohydrates and proteins. These acids compose the 3 major macro-molecules essential for all known life forms.
Structure

Most DNA molecules consist of two bipolymer stands coiled around each other forming a double helix. These two strands are known as polynucleotides due to the fact they are composed of simpler units known as nucleotides. Each nucleotide is composed of a nitrogen-containing nucleobase, either cytosine, guanine, adenine or thymine. These nucleobases are the essential sites where biological information is stored in genetic codes.

How DNA carries information
DNA normally occurs in eukaryotes as linear chromosomes and in prokaryotes as circular chromosomes. The set of chromosomes present in a cell makes up its genome, with the human genome having approximately 3 billion base pairs arranged in 46 chromosomes. The information carried is normally held in pieces of sequence called genes. For genetic information to be transmitted in a gene, the bases have to be paired. The pairing often involves adenine with thymine and guanine with cytosine. There are two ways via which information can be transmitted in a gene. First, when a cell uses the information in a gene, the DNA sequence is copied into a complimentary RNA nucleotides, and then the copy used to make a matching protein sequence through a process called translation. Alternatively, a cell may simply copy its genetic information through a process called DNA replication.
Importance of DNA
The first importance is of course heredity. In this regard, DNA has been used in the legal and medical fields to determine the paternity of a child.
DNA is also used in the early diagnosis of diseases, thereby providing for a pathway to formulate drugs to treat these diseases, as well as prescribe treatment early enough.
It is also a crucial element in the field of forensic science and agriculture, where it's used to determine the criminal culpability of suspects and controlling breeding respectively.