HK408 gene expression in 18 tissues. Numbers of HK408 genes detected in each tissue are compared between microarray and EST data (A). Tissues are ranked from the poorly-sampled (left) to the highly-sampled (right) according to the EST data. The numbers of detected HK408 genes are plotted against the numbers of sampled ESTs for the 18 tissues (B). The sampling growth curve is fitted by Hill function f(x) = axb/(c+xb) with a = 405.0, b = 2.4, c = 7.0e+10. Five tissues — muscle, ovary, heart, thymus and thyroid — are poorly sampled, primarily accounting for the absence of HK408 genes. The expression breadth of HK408 is predominantly enriched at the value 18 in the EST data (C) whereas a messy tail is observed across all breadth groups in microarray data, indicating a noisy nature and high FP rate (D).