Distribution of 3' alternative splicing at positions ranging from two to twenty nucleotides from the dominant splice site. Schematic representation of three groups of 3' alternative splicing occurring close to the dominant site: 3'-AS_dominant site (black line), 3'-AS_proximal site (blue dashed line) and distal site (red dashed line). The brown squares indicate the total number of alternative splices at the 3' splice sites. Alternative splicing at the proximal splice site (intronic splice site) and the distal splice site (exonic splice site) is indicated by triangles and circles. The numbers of each of the three groups of alternative splicing occurring within six nucleotides of the dominant splice site are indicated in the top panel and the percentage in each group was determined as (number of alternative splices within six nucleotides of the dominant site)/(total number of alternative splices within 20 nucleotides of the dominant splice site) × 100. The red asterisks indicate that alternative splicing occurred at in-frame sites.