Association efficiency and linkage disequilibrium parameters for 12 SNPs at the TNF locus. (a) AEA, Gambia; (b) AEA, Malawi; (c) linkage disequilibrium, Gambia; (d) linkage disequilibrium, Malawi. The apparent relative risk at the marker allele indicated in the leftmost column is given when the hypothetical disease allele indicated in the bottom row is assigned a relative risk of 10. In (a,b) color indicates the magnitude of the apparent relative risk: blue indicates a relative risk of less than twofold, yellow between two- and fourfold, and red between fourfold and the maximum of 10-fold. In (c,d) red indicates p < 0.05 by the chi-squared test, uncorrected for multiple tests.