RÉSUMÉ
Objective To study Ax subgroup’s molecular characteristics in Chinese Han population. Methods Eight samples suspected as Ax subgroup were analyzed and duplex PCR RFLP test was used to determine the primary ABO genotypes. These samples were then analyzed by another PCR RFLP test to identify whether there was an nt646 “T” to “A” mutation within the exon 7 of ABO gene, which was a known mutation related to most Ax phenotypes. Samples with discrepancy between serological and gene typing were chosen for further T A cloning and sequence analysis. Results Four out of all tested samples had the known nt646 “T” to “A” mutation. An A *weak01 allele including nt407 and nt467 “C” to “T” mis sense mutation was detected in this study. Moreover, a novel Ax allele with a new single nucleotide C to T mutation was detected at nt745. Another 2 unrelated samples were suspected as AxB through serological test, both of which contained higher quantities of anti A and showed strong agglutination with anti H. And their initial genotypes were BO, and sequence analysis clarified that both had normal O gene and novel nt640 “A” to “G” mutation in their B alleles. Conclusion The novel Ax alleles, one kind of novel B(A) allele and one A *weak01 allele in Chinese Han individuals,have been detected. B(A) phenotypes should have their molecular biology bases as well as other ABO subgroups.