We have assigned the gene (B2m) coding for murine beta 2-microglobulin (B2M) to 
mouse chromosome 2 by using a novel panel of Chinese hamster-mouse somatic cell 
hybrid clones. Because of 35 independent primary hybrids used in this study were 
derived from two types of feral mice, each with a different combination of 
Robertsonian translocation chromosomes, as well as from mice with a normal 
complement of acrocentric chromosomes, analysis of 16 selected mouse enzyme 
markers provided data on the segregation of all 20 mouse chromosomes in these 
hybrids. Mouse B2M was identified in cell hybrids by immunoprecipitation with a 
species-specific anti-mouse B2M antiserum followed by two-dimensional 
polyacrylamide gel electrophoresis of the immunoprecipitated polypeptides. 
Enzyme analysis of the segregant clones excluded all chromosomes for B2m 
assignment except mouse chromosome 2, and karyotype analysis of nine informative 
hybrid clones confirmed the assignment of B2m to this chromosome. These results 
demonstrate that, in the mouse, as in man, B2m is not linked to the major 
histocompatibility or immunoglobulin loci.