Variations of GC3 content in <i>S. cerevisiae</i> protein-coding sequences.

<p>The mean GC3 contents (A) or (B) of 66-codon segments are plotted as a function of the positions or relative to the ATG or to the stop codon, respectively, on which the segments are centered. For a given position or , and are averaged over classes of genes binned by their lengths. The genes of set 1 (, blue dotted line) contain 3 to 5 66-codon segments, the genes of set 2 (, blue dashed line) contain 6 to 8 segments, the genes of set 3 (, blue dot-dash line) contain 9 to 11 segments, the genes of set 4 (, blue long-dash line) contain 12 to 14 segments, and the genes of set 5 (, blue solid line) contain at least 15 segments. Only the average values for the segments common to all the genes of a given set are plotted (<i>i.e.</i> only the segments corresponding to the shortest genes of the set). The thick, red, solid lines represent the mean or averaged over all genes containing at least one 66-codon segment (). The thin, red, solid lines represent the mean theoretical values or averaged over all genes containing at least one 66-codon segment and whose values of and could be determined (). and were calculated as functions of , , and using Equations 7 and 8 (and the estimates of , , and given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0016109#pone-0016109-t001" target="_blank">Table 1</a>), and averaged over segments with the same position or , respectively.