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THE FOURTH LAW OF BEHAVIOR GENETICS 26 Figure 1. Number of schizophrenia-associated SNPs clearing the strict GWAS significance threshold (p< 5×10–8) as a function of discovery-stage sample size, which has increased over time. Although the four studies presented are not methodologically identical (because of different ratios of cases to controls), the increasing number of “hits” with sample size is nevertheless informative.
THE FOURTH LAW OF BEHAVIOR GENETICS 27 Figure 2. Estimated total number of SNPs associated with five disease phenotypes based on results of genome-wide association studies (based on a figure in Ripke et al., 2013). rheumatoidarthritisceliacdiseasecoronary arterydiseasetype 2diabetesschizophreniaESTIMATED NUMBER OF TRAIT-ASSOCIATED MARKERS02000400060008000
THE FOURTH LAW OF BEHAVIOR GENETICS 28 Figure 3.The strong agreement between genetic effects on 28 diseases estimated in Europeans and East Asians (reproduced from Marigorta & Navarro, 2013). The x-axis corresponds to the increment in the odds (on a logarithmic scale) of suffering from the disease for each additional copy of the reference allele, as estimated in Europeans. The y-axis corresponds to the same quantity estimated in East Asians. The increment in log(odds) is the equivalent of the “additive effect” for dichotomously scored traits such as disease status (affected versus unaffected). The gap in the data on the x-axis results from the fact that non-significant genetic effects would have odds ratios near 1 (and thus logarithms of 0) and therefore would not be included in the results of European samples.