MN Blood Group system in Humans

The MN blood group system is under the control of an autosomal locus found on chromosome 4, with two alleles designated L^M and L^N. The bloodtype is due to a glycoprotein present on the surface of red blood cells, which behaves as a native antigen. Phenotypic expression at this locus is codominant because an individual may exhibit either one or both antigenic substances. Frequencies of the two alleles vary widely among human populations.