Nucleic acid double helix

In molecular biology, the term double helix refers to 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 term entered popular culture with the publication in 1968 of The Double Helix: A Personal Account of the Discovery of the Structure of DNA, by James Watson.

The DNA double helix polymer of nucleic acid, held together by nucleotides which base pair together. In B-DNA, the most common double helical structure, the double helix is right-handed with about 10–10.5 base pairs per turn. This translates into about 20-21 nucleotides per turn. The double helix structure of DNA contains a major groove and minor groove. In B-DNA the major groove is wider than the minor groove. Given the difference in widths of the major groove and minor groove, many proteins which bind to B-DNA do so through the wider major groove.

Helix

A helix (pl: helixes or helices) is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helices are coil springs and the handrails of spiral staircases. A "filled-in" helix – for example, a spiral ramp – is called a helicoid. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, and many proteins have helical substructures, known as alpha helices. The word helix comes from the Greek word ἕλιξ, "twisted, curved".

Types

Helices can be either right-handed or left-handed. With the line of sight along the helix's axis, if a clockwise screwing motion moves the helix away from the observer, then it is called a right-handed helix; if towards the observer, then it is a left-handed helix. Handedness (or chirality) is a property of the helix, not of the perspective: a right-handed helix cannot be turned to look like a left-handed one unless it is viewed in a mirror, and vice versa.

Double

Double may refer to:

People

Mathematics and computing

Francis Crick

Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004) was a British molecular biologist, biophysicist, and neuroscientist, most noted for being a co-discoverer of the structure of the DNA molecule in 1953 with James Watson. Together with Watson and Maurice Wilkins, he was jointly awarded the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material".

Crick was an important theoretical molecular biologist and played a crucial role in research related to revealing the genetic code. He is widely known for use of the term "central dogma" to summarize the idea that genetic information flow in cells is essentially one-way, from DNA to RNA to protein.

During the remainder of his career, he held the post of J.W. Kieckhefer Distinguished Research Professor at the Salk Institute for Biological Studies in La Jolla, California. His later research centered on theoretical neurobiology and attempts to advance the scientific study of human consciousness. He remained in this post until his death; "he was editing a manuscript on his death bed, a scientist until the bitter end" according to Christof Koch.

James Watson

James Dewey Watson (born April 6, 1928) is an American molecular biologist, geneticist and zoologist, best known as one of the co-discoverers of the structure of DNA in 1953 with Francis Crick. Watson, Crick, and Maurice Wilkins were awarded the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material".

Watson earned degrees at the University of Chicago (B.S., 1947) and Indiana University (Ph.D., 1950). Following a post-doctoral year at Copenhagen University with Herman Kalckar and Ole Maaloe, Watson next worked at the University of Cambridge's Cavendish Laboratory in England, where he first met his future collaborator and friend Francis Crick.

From 1956 to 1976, Watson was on the faculty of the Harvard University Biology Department, promoting research in molecular biology. From 1968 he served as director of Cold Spring Harbor Laboratory (CSHL) on Long Island, New York, greatly expanding its level of funding and research. At CSHL, he shifted his research emphasis to the study of cancer, along with making it a world leading research center in molecular biology. In 1994, he started as president and served for 10 years. He was then appointed chancellor, serving until 2007 when he resigned his position after making controversial comments claiming a link between intelligence and geographical ancestry. Between 1988 and 1992, Watson was associated with the National Institutes of Health, helping to establish the Human Genome Project.