DNA, or deoxyribonucleic acid, is the hereditary material found in all the humans and most of the living organisms. The information encoded in strands of DNA controls the genetic makeup of organisms. DNA is necessary for the production of Proteins, regulation, metabolism, and reproduction of the cell. DNA is nearly similar in all the cells in a living organism. DNA is found primarily in the nucleus of the cell which is called nuclear DNA, but a small amount of DNA is also found in mitochondria which is called mitochondrial DNA or mtDNA.
The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order, or sequence, of these bases, determines the information available for building and maintaining an organism.
DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule and a phosphate molecule. Together, a base, sugar, and phosphate are called a nucleotide.
Nucleotides are arranged in two long strands that form a spiral called a double helix. The structure of the double helix is somewhat like a ladder, with the base pairs forming the ladder’s rungs and the sugar and phosphate molecules forming the vertical side pieces of the ladder.