Schematic representation of the organization of the human

I locus and the structures of the expressedIGnT gene. Three IGnTtranscripts, IGnTA, IGnTB, and IGnTC,which have different exon 1 but identical exon 2 and exon 3 coding regions, are expressed from the human I locus. The coding nucleotides of exons 1A, 1B, and 1C have 925, 919, and 925 bp, respectively, and the common exon 2 and exon 3 have respective coding nucleotides of 93 and 191 bp.