22.2 Nuclear splice junctions are interchangeable but are read in pairs GT-AG rule describes the presence of these constant dinucleotides at the first two and last two positions of introns of nuclear genes Splice sites are the sequences immediately surrounding the exon-intron boundaries 消当GT-AG rule describes the presence of these constant dinucleotides at the first two and last two positions of introns of nuclear genes. Splice sites are the sequences immediately surrounding the exon-intron boundaries. 22.2 Nuclear splice junctions are interchangeable but are read in pairs