Figure 4.

General nucleotide content changes near splice sites in the neighborhood of a varied intron. Differences in the general nucleotide content in the neighborhood of introns >2047 compared with introns 60-127 (Table 1). Increasing intron length correlates with A enrichment of exon sequences flanking the varied intron, and the preceding intron, whereas C enrichment occurs for the following intron. Increasing intron length also correlates with U and C enrichment upstream of the acceptor of the varied intron (pyrimidine tract), whereas U enrichment occurs upstream of the preceding acceptor and C enrichment occurs for the following acceptor. Only significant nucleotide content changes in the various regions are illustrated based on a two-tailed t-test with p > 0.99.