Autosomal recessive inheritance The gene ABCG2, located on chromosome 4q22.1, encodes an ATP-binding cassette transporter protein that carries the Jr(a) antigen. The Jr(a) negative blood type is inherited in an autosomal recessive manner: individuals who are homozygous for a null mutation of ABCG2 express this phenotype. Homozygosity for certain missense mutations, or heterozygosity for a missense mutation and a null mutation, can result in a weak phenotype with decreased expression of Jr(a) antigen. As of 2018, over 25 null and weak alleles of ABCG2 have been described.
Junior blood group system
Augustine blood group system
Sid blood group system
Vel blood group
Rh blood group system
P1PK blood group system
Lan blood group system
Indian blood group system