All three antigens may exhibit mendelian inheritance, mice being antigen positive or antigen negative, but each may also appear in leukemic cells of mice whose inherited genotype was antigen negative. The G_IX-determining gene in LG VIII of AKR mice apparently is equivalent to Gv-1, which determines expression of the same antigen in 129 strain mice, but which in the latter strain is located in LG IX. As the estimated distance of Gv-1 from H-2 in 129 mice is considerable (37 units) further tests are now indicated to assess the possibility of pseudolinkage in this case.

The Fv-1 locus, also located in LG VIII, influences the mouse's titer of MuLV, and might thereby be thought to regulate the G_IX and gs phenotypes of AKR backcross segregants. But the data indicate a discrete LG VIII locus for G_IX, since expression of this antigen is mendelian and independent of infectious virus titer. Since the G_IX and GCSA phenotypes of AKR backcross segregants were invariably concordant, these two antigens must be specified or controlled by closely linked genes, and the latter also is presumably independent of virus titer. The question as to what extent expression of gs antigen in the segregants is secondary to virus production is undecided.