DNA

Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms (with the exception of RNA viruses). The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information. Along with RNA and proteins, DNA is one of the three major macromolecules that are essential for all known forms of life.

DNA is a linear polymer macromolecule composed from four monomeric units called nucleotides. They are connected by ester bond between phosphoric acid and hydroxyl of the sugar deoxyribose. Stable form is represented by double helix where two opposite running chains are bond through base pairing adenine (A) with thymine (T) and guanine (G) with cytosine (C). The sequence of bases forms a genetic code.