In GWAS, millions of common coding and non–coding genetic variants across the genome are tested for association with a trait (panel 2). Functional variants are often not directly genotyped, but can be correlated with genotyped variants due to linkage disequilibrium (in which restricted recombination between loci causes non–random transmission of alleles). Furthermore, functional variants often regulate expression of a nearby gene, rather than changing the coding sequence.16 Thus, GWAS generally do not discover functional variants or genes, but instead identify genetic loci associated with traits. Informatic and functional characterisation is then needed to further identify functional variants and genes.
