In molecular biology

Molecular biology

Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...

, the term double helix refers to the structure formed by double-stranded molecules of nucleic acid

Nucleic acid

Nucleic acids are biological molecules essential for life, and include DNA and RNA . Together with proteins, nucleic acids make up the most important macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information...

s such as DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 and RNA

RNA

Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

. The double helical structure of a nucleic acid complex arises as a consequence of its secondary structure

Nucleic acid secondary structure

The secondary structure of a nucleic acid molecule refers to the basepairing interactions within a single molecule or set of interacting molecules, and can be represented as a list of bases which are paired in a nucleic acid molecule....

, and is a fundamental component in determining its tertiary structure

Nucleic acid tertiary structure

300px|thumb|upright|alt = Colored dice with checkered background|Example of a large catalytic RNA. The self-splicing group II intron from Oceanobacillus iheyensis....

. The term entered popular culture with the publication in 1968 of The Double Helix: A Personal Account of the Discovery of the Structure of DNA

The Double Helix

The Double Helix: A Personal Account of the Discovery of the Structure of DNA is an autobiographical account of the discovery of the double helix structure of DNA written by James D. Watson and published in 1968. It was and remains a controversial account...

, by James Watson.

The DNA double helix is a spiral polymer

Polymer

A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

 of nucleic acids, held together by nucleotides which base pair together.