ABO BLOOD GROUP SYSTEM LECTURE SLIDE 086: The presence and absence of the O allele-specific single nucleotide deletion result in the cleavage sites of the restriction enzymes, KpnI and BstEII, respectively. Using RFLP and Southern hybridization of genomic DNAs from the cells that were used for the cDNA library constructions, the presence or absence of the single nucleotide deletion was examined. The BstEII digested 2 alleles of MKN45 cells and SW48 cells and 1 allele of SW1417 cells.