How do you sequence an entire genome?
The first genome sequenced was the genome of a bacterium that causes bacterial influenza, Haemophilus influenzae. This bacterial genome was sequenced in 1995, using shotgun sequencing whereby you randomly sequence short fragments of the genome
and then reassemble using bioinformatics tools . When the Human Genome Project sequenced the first human genome in 2001, shotgun sequencing was also used, but, since the human genome is so much larger than a bacterial
genome, the human genome was not fully sequenced. Part of the problem was the time required to perform shotgun sequencing. Next generation sequencing allows sequencing reactions to be completed in a much shorter amount of time. Whole genome sequencing involves extracting DNA from an organism’s tissue, preparing a library by adding adapters that attach the DNA to the sequencing machine, determining the sequence of the
DNA using a machine, and lastly, using bioinformatics to interpret the sequencing results. The sequencing step is usually performed on Illumina sequencing machines. Sequencing starts with single-stranded DNA and fills in the opposite strand, using
fluorescence to identify each base, or molecule of DNA, as it is added to the strand.
Benefits of whole genome sequencing
WGS provides the most comprehensive data about a given organism. Using next generation sequencing can deliver large amounts of data in a short amount of time. Since you are profiling the entire genome, it allows for the discovery of previously unknown
genes or variants. As scientists work toward precision medicine and personalized treatment, WGS may point to genes that do not cause disease but could aid in choosing the best therapy for an individual. WGS could even reveal genetic predispositions
that could be mediated through lifestyle or environmental changes to aid in prevention.