The allele frequencies and the polymorphism in the ABO blood group gene of 340 individuals living in the central part of Japan near Tokyo were analyzed using polymerase chain reaction (PCR) based techniques. We analyzed the known polymorphic sites (at positions 297, 526, 657, 703, 796, 803 and 930) between A and B alleles, and the single deletion at position 261 in 0 alleles using PCR-RFLP (restriction fragment length polymorphism), PCR-SSCP (single strand conformation polymorphism) and sequencing methods. We found two new allele subtypes in the A and B alleles. A new A allele subtype showed four nucleotide differences at positions 297 (adenine versus guanine), 526 (cytosine versus guanine), 657 (cytosine versus thymine) and 703 (guanine versus adenine), and the allele frequency was 0.0044. This A allele subtype was probably generated by a crossing-over of B allele and A or 0 allele. Second new B allele subtype had a single nucleotide difference at position 467 (cytosine versus thymine) and the frequency was 0.0015. The ratio of a mutant O allele (the nucleotide differences at positions 646, 681, 771 and 826) to the common 0 allele in the central part of Japan was low in the western part (Osaka region) and higher in the northern part (Yamagata region). There may be a geo-graphical cline for these two allele frequencies in Japan. There was no difference in the transferase activities between common alleles and rare alleles.
The Anthropological Society of Nippon