Abstract
The International HapMap Project was proposed in order to quantify linkage disequilibrium (LD) relationships among human DNA polymorphisms in an assortment of populations, in order to facilitate the process of selecting a minimal set of markers that could capture most of the signal from the untyped markers in a genome-wide association study. The central dogma can be summarized by the argument that if a marker is in tight LD with a polymorphism that directly impacts disease risk, as measured by the metric r2, then one would be able to detect an association between the marker and disease with sample size that was increased by a factor of 1/r2 over that needed to detect the effect of the functional variant directly. This ‘fundamental theorem’ holds, however, only if one assumes that the LD between loci and the etiological effect of the functional variant are independent of each other, that they are statistically independent of all other etiological factors (in exposure and action), that sampling is prospective, and that the estimates of r2 are accurate. None of these are standard operating assumptions, however. We describe the ramifications of these implicit assumptions, and provide simple examples in which the effects of a functional variant could be unequivocally detected if it were directly genotyped, even as markers in high LD with the functional variant would never show association with disease, even in infinite sample sizes. Both theoretical and empirical refutation of the central dogma of genome-wide association studies is thus presented.
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Acknowledgements
Grant MH63749 from the National Institutes of Mental Health, along with funding from the Sigrid Juselius Foundation, the Academy of Finland, The Finnish Cultural Foundation, and the Burroughs-Wellcome Fund is gratefully acknowledged. r2 estimates for pairs of SNPs on all Chromosomes from CEU, CHB, JPT and YRI datasets, release date June 16th 2005, from the International HapMap Consortium were used for Figure 2, and as such the consortium is acknowledged. Thanks to Harald H.H. Göring for critical comments on the manuscript.
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Appendix
Appendix
Demonstration that multiplicativity of correlation coefficients implies conditional independence.

Since

then ρAC=ρAB ρBC if and only if

Expanding the right side of this equation leads to the following:

However, if we expand the left side of the equation,

and according to the Chain rule from elementary probability, this implies that

but this only equals the right side of Eq. (1) above, if we assume that we have conditional independence of A and C when B is true, such that, for example, P(A∣BC)=P(A∣B).
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Terwilliger, J., Hiekkalinna, T. An utter refutation of the ‘Fundamental Theorem of the HapMap’. Eur J Hum Genet 14, 426–437 (2006). https://doi.org/10.1038/sj.ejhg.5201583
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DOI: https://doi.org/10.1038/sj.ejhg.5201583
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