Sometimes the double helix likes to mix it up! Scientists at the University of Cambridge, United Kingdom, have found that DNA at the end of chromosomes actually have a very different structure: instead of double-stranded, they have four strands.
Balasubramanian's group has been pursuing a four-stranded version of the molecule that scientists have produced in the test tube now for a number of years.
It is called the G-quadruplex. The "G" refers to guanine, one of the four chemical groups, or "bases", that hold DNA together and which encode our genetic information (the others being adenine, cytosine, and thymine).
The G-quadruplex seems to form in DNA where guanine exists in substantial quantities.
Jonathan Amos of BBC has the post: Link