Analysis of length differences between orthologous pairs of unequal exon length. A. Distribution of remainders of three in length differences between orthologous exon pairs with unequal length. The MOD 3 = 0 category means that the remainder is zero when the length difference between exon orthologs is divided by three, and so on. The x-axis is the region in which the united exon is located, and the y-axis indicates the percentage of orthologous pairs with unequal length in each region for each category. B. Distribution in counts of united exons where length difference is less than or equal to 30 base pairs compared to orthologous exon pairs.