Chromosome on ABO blood group is

Histo-blood group ABO system transferaseis an enzyme with glycosyltransferaseactivity, which is encoded by the ABO genein humans. It is ubiquitously expressed in many tissues and cell types. ABO determines the ABO blood group of an individual by modifying the oligosaccharides on cell surface glycoproteins. The ABO gene resides on chromosome 9 at the band 9q34.2 and contains 7 exons. The ABO locus encodes three alleles. The A allele produces a-1,3-N-acetylgalactosamine transferase (A-transferase), which catalyzes the transfer of GalNAc residuesfrom the UDP-GalNAc donor nucleotide to the Gal residues of the acceptor H antigen, conveing the H antigen into A antigen in A and AB individuals. The B allele encodes a-1,3-galactosyl transferase (B-transferase), which catalyzes the transfer of Gal residues from the UDP-Gal donor nucleotide to the Gal residues of the acceptor H antigen, conveing the H antigen into B antigen in B and AB individuals.