Humans, strawberries, honeybees, chickens and rats are among the many organisms to have their DNA sequenced. But although sequencing an individual species is challenging, it is much harder to sequence the DNA of a single cell.
To get enough DNA for sequencing, thousands or even millions of cells are usually required. And finding out which mutations are in which cells is almost impossible, and mutations present in only a few cells (like early cancerous cells) are hidden altogether. But a technique reported today in Science1 provides a way to copy DNA so that more than 90% of the genome of a single cell can be sequenced. The method also makes it easier to detect minor DNA sequence variations in single cells and, so, to find genetic differences between individual cells. Such differences can help to explain how cancer becomes more malignant, how reproductive cells emerge and even how individual neurons differ.