Scientists have discovered that DNA behaves in an unexpected way when moving through tiny sensors, overturning decades of assumptions about how genetic material tangles. New research reveals that what were once thought to be random knots are actually organized, twisted coils known as plectonemes.
The study, led by researchers at the University of Cambridge, identified these plectonemes as a “hidden player” in DNA behavior. These structures form when DNA is pulled through a nanopore, a microscopic opening used to read genetic sequences. The findings suggest that these coils could redefine how experts understand DNA organization and improve the accuracy of future medical diagnostics.
Understanding the Difference Between Knots and Coils
For years, researchers observed unusual fluctuations in electrical signals when DNA passed through nanopores. They generally attributed these messy signals to knots, comparing them to tangled shoelaces that disrupt the flow of data. However, the new findings indicate that these disruptions are frequently plectonemes—structures where the DNA twists around itself like a coiled phone cord.
The distinction between the two is vital for interpreting genetic data. While knots are tightened by physical pulling forces and tend to be short-lived, plectonemes can grow larger and persist much longer. By recognizing these differences, scientists can now read DNA signals with much higher precision than was previously possible.
The Role of Ionic Flow and Torque
The formation of these plectonemes is driven by a process called electroosmotic flow. As DNA threads through a nanopore, the movement of fluid and ions inside the pore causes the DNA strand to spin. This rotation builds up a twisting force, or torque, which travels along the molecule and causes it to coil into plectonemes.
To confirm this mechanism, the research team conducted computer simulations and experimental tests. They engineered a specific type of “nicked” DNA, which contained small breaks at precise intervals. These nicks allowed the DNA to rotate more freely, preventing the buildup of torque and significantly reducing the number of plectonemes that formed. This experiment proved that the coiling was a direct result of the twisting forces within the pore.
New Opportunities for Medical Diagnostics
Being able to distinguish between knots and plectonemes opens new doors for genomic technology and biosensing. Knots typically pass through a nanopore quickly, creating a brief “bump” in the electrical signal. In contrast, plectonemes linger, leaving behind a distinctive and extended electrical fingerprint.
Experts believe this discovery will allow for more nuanced readouts of DNA integrity. By monitoring how these structures form and behave, scientists could potentially identify DNA damage more effectively. This could lead to the development of a new generation of biosensors capable of early disease detection by spotting subtle changes in the way DNA organizes itself.
Future Impacts on Genomic Science
The implications of this research extend beyond the laboratory and into the core of how cells function. In nature, plectonemes and knots are regularly created by enzymes during essential biological processes like replication and transcription. Understanding how these entanglements form under natural pressure helps researchers grasp how the genome maintains its stability and order within a cell.
As genomic technologies continue to evolve, the ability to control and detect these twist structures may offer a clearer picture of chromosome health. This long-overlooked structural feature is now taking center stage, promising to shift the focus of genetics research toward a more detailed understanding of the “twisted” nature of life.
