Molecular analysis of the O alleles at the blood group ABO locus in populations of different ethnic origin reveals novel crossing-over events and point mutations

The blood group ABO genotypes of 138 group O individuals with three different ethnic origins in Brazil were determined, including Whites, Blacks and Amerindians. Several previously undescribed O alleles were found, predominantly in the Black group, in which about a third of the samples did not conform to previously known O allele structures. It has been well documented for the first time that some new alleles can arise from crossing-over events between known alleles in the ABO system. This was made possible by both restriction endonuclease analysis and direct sequencing of exons 3-7 in the ABO gene. The anticipated relatively high frequency of some of these new alleles in certain populations, necessitates great care when interpreting results from existing genotype screening methods. (C) 1997 Academic Press.