Acronym for “deoxyribonucleic acid”, the chemical that carries the genetic information of most biological organisms
The building blocks of DNA are called “nucleotides”, each comprising a sugar (deoxyribose), phosphoric acid, and a base. There are four bases, adenine (A), cytosine (C), guanine (G) and thymine(T), which are always arranged in pairs, A matches up with T and C matches up with G.
These building blocks are assembled to form giant molecules (about two metres long in humans) of two intertwined helical strands of nucleotides, the famous “double helix”.
The sequence of nucleotides carries an organism's entire genetic code, which is fully present in every cell.
The two strands are held together by pairing of complementary bases. The complementation of opposing base pairs forms the basis upon which DNA is duplicated during cell division. The two strands first separate like the two halves of a zipper; each of them then acts as a template upon which a new complementary strand is formed.
The information in DNA is read in a process called “transcription”. The DNA strands separate to expose the site of expression, enabling the relevant information for the synthesis of a protein to be replicated in the form of a related molecule: RNA (ribose nucleic acid). The information obtained by transcription is used throughout the cell to synthesise proteins. The discrete, functional unit of DNA encoding the information to make a certain protein is a called a “gene”.
In 1953, a molecular structure for DNA was proposed by James Watson and Francis Crick. Since the beginning of the 1970s, it has been possible to cut DNA molecules at defined sites with the help of restriction enzymes. They may then be reassembled, forming novel combinations (see “recombination”).