Scientists at Cambridge University in Britain say they have found evidence of a four-stranded version of DNA at work in human cells.
They say the discovery could lead to new ways to fight cancer.
In 1953, James Watson and Francis Crick famously revealed the structure of DNA, showing how two long chemical chains wound up around each other to encode the information that cells need to build to maintain our bodies.
Now, Cambridge scientists have for the first time detailed instances where a four-stranded DNA structure will form in human cells, the BBC reports.
They told the journal Nature Chemistry that the shape often appears in rapidly dividing cells, such as cancerous ones.
They suggest that if the structure can be contained, it might be possible to block the runaway cell proliferation that drives cancers.