The MN blood group in humans is under the control of a pair of co-dominant alleles, LM and LN. Most people in the Eskimo population are M/M, while this genotype is rare among Aborigines. In fact, they tend to possess the opposite genotype (N/N).
The MN blood group system is under the control of an autosomal locus found on chromosome 4 out of 23, with two alleles designated LM and LN. The blood type 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.[1]