For complex traits and diseases, there are many GWAS loci which could not be replicated across different ethnicities, such as the SNP rs7756992 in the CDKAL1 gene which strongly associates with T2D in subjects of European ancestry, but displayed no association in a population of West Africa (Steinthorsdottir et al., 2007). Here, CDKAL1 is linked to type 2 diabetes mellitus.