Often, large sample sizes are needed to uncover rare genetic variants associated with disease traits. In fact, this realization — from the first generation of exome discovery studies — is driving new interest in ultracheap genotyping arrays (collections of targeted fragments of DNA). Using such arrays, geneticists can speed up the sequencing process and analyse many targeted samples in one go. Exome sequencing combined with the use of genotyping arrays is likely to be the favoured approach over the next decade. Nonetheless, GWAS remains a useful precursor to such studies, as well as to those involving whole-genome sequencing.
