Electrophoresis – which separates the molecules in a solution by their size and electrical charge – is then used to check the quality and quantity of the DNA obtained.
Next-generation-sequencing (NGS) methods – which can read the sequence of many thousands of DNA pieces at once – have massively speeded up the sequencing of whole genomes. Several methods are available, including those created by Illumina, Oxford Nanopore and Pacific BioSciences.
Most NGS methods first require the creation of a ‘library’ of small fragments of DNA from the extracted sample, which together represent the whole genome of the organism. Each of the fragments in the library is treated (e.g., by the addition of small ‘adaptor’ sequences to its ends) to enable it to be ‘read’ by the sequencing machine.