A genome is the entire DNA sequence of an organism. The DNA contains the instructions for how a living organism is formed. Whole genome sequencing (WGS) is a next generation sequencing application that determines the entire DNA sequence all at once. The alternative to WGS is targeted next generation sequencing, which sequences part of the genome.
Since WGS starts with DNA, you first need to extract DNA from your tissue or cell sample. How much DNA is needed for whole genome sequencing? WGS can be performed with as little as 100 ng of DNA. If you don’t need data from the whole genome, targeted sequencing can be performed with as little as 1 ng of DNA. You will need to prepare libraries using a library preparation kit and adapters. Adapters may come with barcodes, or indexes, that help identify the sample or specific molecules in the sample and aid in multiplexing. Since sequencing machines are very expensive, sequencing services can carry out the sequencing step for you. Analysis can be performed with a variety of available free bioinformatics tools.
Variants are also called mutations and are points in the genome that differ between organisms. WGS can be used to determine variant frequencies, or how often a difference occurs within populations of organisms, and to associate genetic variants with disease through genome-wide association studies (GWAS). In a GWAS, WGS on two populations is done to compare trait differences with genetic differences—to associate identified traits with identified variants. WGS was first used for clinical diagnostics in 2009, but time and costs have limited its use in this area [2, 3]. As the price of WGS decreases, it is becoming more common as a diagnostic tool. Having achieved the “$1000 genome”, multiple companies are pushing towards the next goal of the “$100 genome” [4–6].
Read our articles about whole genome sequencing.