After analyzing the secondary structures of 68 exon-intron-exon and the corresponding exon-exon sequence segments, it is found that about 90% of 5′ and 3′ terminal bases G (splicing sites) of introns are situated in the loops of secondary structures or at the ends of stems near the loops, and most of “G”s in loops are closed to the ends of loops. Approximately 92% of the connecting sites of the adjoining exons also show the similar features. About 82% of the branch point “A”s are situated in loops or at the ends of stems near the loops. Splicing sites and branch points approach each other in space because of the folding.