DNA in a Twist?

dna structureWhat does DNA look like? Ask anybody who’s studied biology over the last 50 years and they’ll instantly tell you about its double helix structure.  A few might also remember that it consists of a twisting ladder of base pairs constructed of adenine coupled with thymine and cytosine with guanine . (A, T, C, G)

The now-ubiquitous double-helix structure was first published in the journal Nature in 1953 by scientists James Watson and Francis Crick from the University of Cambridge. In 1962, the pair were awarded The 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”.

Now, nearly 60 years later, scientists from the same institution have published a paper in the same journal, but their results suggest that there may be more to the structure of DNA than their predecessors thought.

quadruple-helixThe new study  presents evidence that some human DNA may actually have four strands instead of two. There is also evidence that the quadruple helix may be linked to cancer.

Researchers have been searching for quadruple-helix DNA for the better part of a decade. They knew such structures existed in microscopic ciliates, but had never observed them in humans. However, by building antibodies that bind to the four-stranded structure, the Cambridge team was finally able to pin down the existence of the quadruple helix in human DNA and pinpoint its location on individual chromosomes.

The quadruple helix forms in the presence of unusually high levels of guanine.  They also found that it forms during the phase of DNA replication when the genetic material is being copied, and that the number of quadruple-helices increased with each replication. The growth is somewhat similar to that of cancer, which alters the genetic code to increase DNA replication and cause tumor growth.

Understanding the helix’s structure and function may well be key to solidifying its association with cancer. If proven true, researchers may one day treat the disease by making structure-specific antibodies to block the replication response that causes tumors.

Now that’s worth getting ourselves in a twist about!

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