The XG antigen is a

red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

surface

antigen In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

discovered in 1962. by researchers at the

MRC Blood Group Unit The MRC Blood Group Unit, originally the Blood Group Research Unit, was a research unit of the British Medical Research Council from 1946 to 1995. Initially established in the Lister Institute, it transferred to the Galton Laboratory (the Genetics ...

.Mann, J. D., Cahan, A., Gelb, A. G., Fisher, N., Hamper, J., Tippett, P., Sanger, R., Race, R. R A sex-linked blood group. Lancet. 1962;279:8. The PBDX gene that encodes the

is located on the short arm of the

X chromosome The X chromosome is one of the two sex-determining chromosomes ( allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO se ...

. Since males normally have one X chromosome they are considered hemizygotes. Since women have two copies of the gene and could be

heterozygotic Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mo ...

for the presence or absence of the functioning gene they could (through the process of lyonisation)

express Express or EXPRESS may refer to: Arts, entertainment, and media Films * '' Express: Aisle to Glory'', a 1998 comedy short film featuring Kal Penn * '' The Express: The Ernie Davis Story'', a 2008 film starring Dennis Quaid Music * ''Express'' ...

the functioning

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

on just some of their red blood cells.

Frequency

References

Blood antigen systems {{cell-biology-stub Transfusion medicine