We have isolated human genomic DNA clones encompassing 30 kbp of the h
isto-blood group ABO locus. The locations of the exons have been mappe
d and the nucleotide sequences of the exon-intron boundaries have been
determined. The human ABO genes consist of at least seven exons, and
the coding sequence in the seven coding exons spans over 18 kb of the
genomic DNA, The exons range in size from 28 to 688 bp, with most of t
he coding sequence lying in exon 7.