If the largest effect sizes are so small, hundreds of such associations will be needed to account for the heritability of a common disorder or quantitative trait. If these associations of very small effect size can be detected, it would not matter if trait-specific microarrays included hundreds or even thousands of SNPs in order to predict various aspects of a trait, its developmental changes, its interactions and correlations with the environment and all of these in different populations (Janssens, Aulchenko, Elefante, Borsboom, Steyerberg et al., 2006; Khoury, Little, Gwinn, & Ioannidis, 2007). Microarrays could be the new diagnostic manuals of the future, at least in relation to genetic risk.
