XG Human

The XG blood group system consists of one identifiable antigen, Xg^a, and two phenotypes: Xg(a+) and Xg(a−) . The system follows the pattern of sex-chromosome inheritance, meaning that daughters can inherit the gene for Xg^a from either parent, while sons can only inherit it from their mother . The frequency of the Xg(a+) phenotype varies among different populations, with approximately 65% of white males and 90% of white females expressing this antigen .

The discovery of the XG blood group system greatly aided the mapping of the X chromosome. It was the first blood group to be mapped to the human X chromosome, specifically to the pseudoautosomal region of the X (Xp22.33) and Y (Yp11.2) chromosomes . This mapping has been instrumental in studying sex-linked traits and understanding the mechanisms underlying sex chromosome disorders such as Turner and Klinefelter syndromes .

Recombinant human XG blood group proteins are produced using recombinant DNA technology. This involves inserting the gene encoding the XG antigen into a suitable host cell, such as bacteria or yeast, which then produces the protein. These recombinant proteins are essential tools in research and diagnostic applications. They are used to study the structure and function of the XG antigen, as well as to develop assays for detecting XG antigens in blood samples .

Unlike other blood group systems, the XG blood group does not have a strong relationship with clinically recognized outcomes. It does not play a significant role in transfusion compatibility or susceptibility to infectious diseases . However, its importance lies in its contribution to genetic research and its use as a marker for mapping sex-linked traits .