What is a Double Helix?

Niki Foster
Niki Foster

A double helix is a geometrical shape consisting of two helices around the same axis. A helix is a twisting spiral shape, like a spring. The two helices in this shape are congruent, meaning that they are the same in every dimension, though in different positions around the axis. A double helix may be either right-handed or left-handed, depending on whether it coils clockwise or counter-clockwise, respectively.

DNA takes the form of a double helix.
DNA takes the form of a double helix.

The structure is probably best known as the shape of deoxyribonucleic acid (DNA), the material that carries genetic information in the body. The DNA double helix is right-handed and consists of two strands or backbones of phosphate and sugar joined by base pairs of the nucleotides adenine, thymine, guanine, and cytosine, often abbreviated A, T, G, and C. Adenine always joins with thymine, and guanine always joins with cytosine, so knowing the bases on one side of the helix reveals those on the other side. These four nucleotides are responsible for encoding all of the genetic information in the human genome. The shape of DNA was first published in 1953 by molecular biologists Francis Crick and James D. Watson.

A double helix is best known as the geometrical shape of DNA.
A double helix is best known as the geometrical shape of DNA.

The helix is a frequently occurring shape in nature, found, for example, in the vines of various plants and in many proteins in the body. Though the double helix is rarer, the shape is not confined to DNA. Another interesting example of it occurring naturally is in the shape of a space nebula in the Milky Way galaxy photographed in 2006.

Scientists believe that this "DNA nebula" was formed by the twisting force of magnetic field lines running through its center. The field lines may be anchored to a body orbiting the black hole at the center of the Milky Way, about 300 light years away from the nebula. Though this nebula is the only known one of its kind, researchers speculate that there are more of them throughout the universe, though possibly not within this galaxy.

Niki Foster
Niki Foster

In addition to her role as a wiseGEEK editor, Niki enjoys educating herself about interesting and unusual topics in order to get ideas for her own articles. She is a graduate of UCLA, where she majored in Linguistics and Anthropology.

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While first published by Watson and Crick, the double helix report they wrote was based on photography and data recorded by Rosalind Franklin, another doctor. Her work was shown to them, without her knowledge, by her supervisor, Maurice Wilkins- several years later, the three men received the Nobel Prize, and she did not.

I believe that this article ought to include her as well as the names of Watson and Crick, who might never be known without her help.


I have a friend who postulated that everything can be measured in double helices, including the forces of nature and the timeline of history. It is an interesting theory, because a helix forms the most basic foundation of life: DNA. History also seems to repeat itself, but in a different manner every time, and so more like a spiral, or helix, than a revolution.


I never even heard of the Double Helix Model until my report on it. I think it's interesting.

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