splicing_variant intron_variant splice_site_variant EBI term - essential splice site - In the first 2 or the last 2 base pairs of an intron. The 5th base is on the donor (5') side of the intron. Updated to b in line with Cancer Genome Project at the Sanger. sequence SO:0001629 http://vat.gersteinlab.org/formats.php 2010-03-24T09:42:00Z kareneilbeck A sequence variant that changes the first two or last two bases of an intron, or the 5th base from the start of the intron in the orientation of the transcript. VAT:spliceOverlap splice site variant essential_splice_site