Journal of Virology
The two murine retroviral restriction genes, Fv-4 and Akvr-1, are very similar in their effects, distributions, ranges of action, and phenotypes. Akvr-1 has been shown to segregate independently in backcrosses with a variety of retroviral restriction loci, including Fv-1, Fv-2, Ril-1, and Ril-2. An allelism test cross of FRG (Fv-4R) x LCRR (Akvr-1R) hybrids mated to AKR mice failed to produce any viremic offspring. These results suggested that Akvr-1R and Fv-4R are alleles of a single locus, Fv-4, on mouse chromosome 12.
O'Brien, Stephen J.; Eric J. Berman; John D. Estes; and Murray B. Gardner. 1983. "Murine Retroviral Restriction Genes Fv-4 and Akvr-1 are Alleles of a Single Locus." Journal of Virology 47, (3): 649-651. https://nsuworks.nova.edu/cnso_bio_facarticles/223