) is a nucleic acid
that contains the genetic
instructions for the development and function of living organisms. All living things contain DNA, with the exception of some viruses
with RNA genomes
. The main role of DNA in the cell
is the long term storage of information. It is often compared to a blueprint, since it contains the instructions to construct other components of the cell, such as proteins
molecules. The DNA segments that carry genetic information are called genes
, but other DNA sequences have structural purposes, or are involved in regulating the expression of genetic information.
DNA is a long polymer of simple units called nucleotides, which are held together by a backbone made of sugars and phosphate groups. This backbone carries four types of molecules called bases and it is the sequence of these four bases that encodes information. The major function of DNA is to encode the sequence of amino acid residues in proteins, using the genetic code. To read the genetic code, cells make a copy of a stretch of DNA in the nucleic acid RNA. These RNA copies can then be used to direct protein synthesis, but they can also be used directly as parts of ribosomes or spliceosomes.
James D. Watson and Francis Crick produced the first accurate model of DNA structure in 1953 in their article The Molecular structure of Nucleic Acids. Watson and Crick proposed the central dogma of molecular biology in 1957, describing how proteins are produced from nucleic DNA. In 1962 Watson, Crick, and Maurice Wilkins jointly received the Nobel Prize.