Alternative genetic mechanisms may also contribute to disease and disruption of the same genes or molecular pathways by different mechanisms are likely to be relevant to the consequent phenotype. Follow-up strategies are increasingly using GWAS results to test other genetic risk mechanisms such as involvement of copy-number variation (CNV), the cumulative impact of CNV burden (e.g., the number of CNVs), and the cumulative impact of hundreds or thousands of SNP genotypes. In addition, investigators are actively working to assess the cumulative impact of individually rare risk alleles and epigenetic phenomena such as methylation.
