Nucleic acid double helix

In molecular biology, the double helix is the structure formed by double-stranded molecules of nucleic acids such as DNA. The double-helical structure of a nucleic acid complex arises as a consequence of its secondary structure, and is a fundamental component in determining its tertiary structure. The DNA double-helix biopolymer of nucleic acids is held together by nucleotides which base pair together.

Source: Wikipedia — Nucleic acid double helix (CC BY-SA 4.0)