Figure 2.

Neighborhood effects on splice site strength. Nucleotide positions D-1, D3, D4, D6, A-6 and A-5 show pronounced changes in information levels when intron or exon lengths are varied (see Figure 1). The figure illustrates the effects at these nucleotide positions of donor and acceptor sites in the neighborhood. The subscript labeling specifies how far the donor or acceptor sites are from the introns or exons being varied, as defined below. (a,b) The average information levels (ave(D-1, D3, D4, D6) or ave(A-6, A-5)) are plotted for (a) nine intron length or (b) seven exon length ranges. (a) The varied introns are flanked by donor D₀ and acceptor A₀. (b) The varied exons are flanked by acceptor A_-1 and donor D₀. Length frequency distributions are shown for (a) the introns flanked by D₀ and A₀ and (b) the exons flanked by A_-1. (c) The figure illustrates the donor and acceptor sites in the neighborhood whose adjacent nucleotide positions showed elevated information with shorter introns or exons (upper arrows) or longer introns or exons (lower arrows). Solid arrows depict strong effects; dashed arrows show weak effects.