APOL1 and kidney disorder: A dominant phenotype can arise via a number of different molecular mechanisms, including a gain-of-function, a gain-of-new-function, haploinsufficiency, dominant negative, loss of heterozygosity and more [37], [38] and therefore definitively testing the underlying molecular mechanisms by which APOL1 G1 and G2 alleles might cause kidney disease would be complex and arduous if the phenotype were semi-dominant.