Involved in oxygen transport from the lung to the various peripheral tissues. Heterotetramer of two alpha chains and two beta chains. Red blood cells. Inbred mouse strains possess 1 of 3 alleles at the HBB locus: D (diffuse), S (single), and P. The D and P alleles are actually closely linked doublets that coordinately express a major and a minor chain, the minor chain being slightly different in the two alleles. The S allele produces only 1 chain, it is characteristic of North American wild mice. The D-minor sequence is shown. See also the entry for the beta D-major chain and the S allele. Belongs to the globin family.