Table 1. Diverse terminal dinucleotides on U12-dependent introns in the human genome.

Intron termini	Reported in Burge et al. (7)	Total found	Putative splicing errors	Total confirmed
GT-AG	34	279	4	275
AT-AC	12	109	1	108
AT-AG	1	8	1	7
GT-AT	0	5	1	4
AT-AT	0	4	0	4
GT-GG	0	7	4	3
AT-AA	1	5	3	2
GT-AA	0	1	0	1
GT-CA	0	1	1	0
GC-AG	1	0	0	0
Totals	49	419	15	404

The total number of U12-dependent introns previously reported in Burge et al. (7), the original total found in this analysis, the total discarded as likely splicing errors and the final confirmed total are shown for a variety of possible intron termini. Genomic scans were also performed for introns with GT-AC, GC-AC, GG-AC, GG-AG, AT-GG and AT-CA termini. No U12-dependent introns were identified in these scans. The AT-AC and GT-AG scans considered target introns with donor site scores greater than nine bits, branch site scores greater than six bits and lengths of <20 kb. All other scans examined introns of up to 2 kb in length. The GT-AC and AT-AG scans used 11 and nine bits as donor and branch scores thresholds, the AT–AA scan used 10 and eight bits and all remaining scans used 10 and seven bits. All scans used a branch site to acceptor site range of 8–21 bp.