Fig. 3

For each internal exon, three states (\(E^{\text {+,H}}_{0}\), E0+,M,E0+,L) are used to model exons of high, medium, and low GC content. This figure only illustrates three internal exon states for one phase on the plus strand (corresponding to one reading frame). The internal exons of other phases, the initial exon, the terminal exon, and the single exon all have three states for high, medium, and low GC content. Genes of various GC contents and gradients can be represented as various paths through the exon states