The double helix has been considered the normal form of DNA for 60 years, since researchers James Watson and Francis Crick described the way two long chemical chains wound up around each other to encode the information that cells need to build and maintain our bodies.
A four-stranded version scientists have been able to produce in test tubes for a number of years has now been found in human cells for the first time, the BBC reported Monday.
Researchers at Cambridge University found the four-stranded DNA arose most frequently during a phase when a cell copies its DNA just prior to dividing.
That could be significant in the study of cancers, they said, which are usually driven by genes that mutate to increase DNA copying.
"The existence of these structures may be loaded when the cell has a certain genotype or a certain dysfunctional state," Shankar Balasubramanian from Cambridge's department of chemistry said.
Control of the structures could provide novel ways to fight cancer, he said.
"We need to prove that; but if that is the case, targeting them with synthetic molecules could be an interesting way of selectively targeting those cells that have this dysfunction."