Double helix

In geometry, a double helix (plural double helices) is two helices with the same axis, but they differ by a translation along the axis. Scientists James Watson and Francis Crick determined that a double shape is in the shape of a twisted ladder. The ladder is made of a backbone of sugar and phosphate groups (DNA consists of three main parts: a 5-carbon sugar, a nitrogenous base, and a phosphate group). The term is most often used in reference to the nucleic acid double helix, the main structure of nucleic like DNA and RNA.