This image compares three DNA sequencing technologies: Sanger sequencing, Massively Parallel DNA sequencing, and Nanopore DNA sequencing. Sanger sequencing (left) sequences 500-700 bases per reaction ...

In a way, sequencing DNA is very simple: There's a molecule, you look at it, and you write down what you find. You'd think it would be easy—and, for any one letter in the sequence, it is. The problem ...