A human blood group system defined by red cell antigens specified by a gene on the long arm of chromosome 4 between bands 28.2 and 31.1. The MN locus encodes a protein called glycophorin A (q.v.), and for this reason the gene symbol has been changed to GYPA. Each human red blood cell has about 500,000 of these proteins embedded in its plasma membrane. The M and N antigens are isoforms of glycophorin A that differ in the amino acids present at only two of the 131 sites.
Subjects: Genetics and Genomics.