Fig. 4.—

Box plots of (a) GC content at 3rd positions (GC3), (b) expression specificity τ, (c) d_s, and (d) d_n for subsets of genes according to their chromosomal positions. Whiskers are drawn as implemented in the R-function box plot (see Materials and Methods). ${}^{***}P\le 0.001$, ${}^{**}P\le 0.01$, ${}^{*}P\le 0.05$.