Linkage analyses of 4 traits. A, CHI3L2 on chr 1. B, GSTM1 on chr 1. C, PSPH on chr 7. D, VAMP8 on chr 2. One linked QTL plus polygenic (magenta, long-dashed), one linked QTL plus one unlinked QTL (blue, dotted), one QTL (black, solid), VC (green, short-dashed), log 10 of Bayes factors (cyan, dot-dashed), and two linked QTLs (red, dot-dot-dashed).