nanopore long-read sequencing
/ NAN-oh-pore /
What if, instead of copying DNA and reading the copies, you could read a single original DNA molecule directly, by threading it through a tiny hole and sensing each base as it passes? That is exactly what nanopore sequencing does. It is a third-generation, single-molecule method, and its signature strength is reading very long stretches of DNA in one go.
A nanopore is a protein channel set in a membrane, with a small ionic current flowing through it. A single strand of DNA is fed through the pore, and as the bases pass through the narrowest point they partly block the current. Different bases (and short combinations of bases) block it by slightly different amounts, so the rise and fall of the electrical current over time is, in effect, a recording that can be decoded back into the sequence. Because you are reading one continuous molecule as it slides through, the read can be enormously long — tens of thousands of bases, sometimes far more — limited mainly by how long a DNA molecule you can deliver intact.
Long reads solve problems short reads cannot: they can span repetitive regions and structural rearrangements, help assemble genomes without gaps, and can even detect chemical modifications like DNA methylation directly from the current signal. The devices can be small and portable, enabling sequencing in the field. The honest trade-off is accuracy: per-base error rates have historically been higher than short-read sequencing by synthesis, though they have improved markedly. In practice, labs often pair long nanopore reads (for structure) with accurate short reads (for fine detail), playing the two methods to their respective strengths.
A field researcher carries a USB-stick-sized nanopore device and sequences a viral genome on a laptop during an outbreak, getting reads long enough to capture whole genes in single passes — something a benchtop short-read machine in a distant lab could not do as quickly.
One DNA molecule threaded through a pore; current dips spell the bases.
Nanopore's superpower is read length, not per-base accuracy — historically it has had higher error rates than short-read synthesis, so for fine single-base calls labs often combine long nanopore reads with accurate short reads.