An endogenous retrovirus presumed to have been endogenized or relocated recently in a marsupial, the red-necked wallaby.

An albino infant wallaby was born to a mother with wild-type body color. PCR and sequencing analyses of (encoding tyrosinase, which is essential for melanin biosynthesis) of this albino wallaby revealed a 7.1-kb-long DNA fragment inserted in the first exon. Since the fragment carried long terminal repeats, we assumed it to be a copy of an endogenous retrovirus, which we named . We cloned other copies residing in the genomes of this species and of another wallaby species. The copies exhibited length variation, and the longest copy (>8.0 kb) contained open reading frames whose deduced amino acid sequences were well aligned with those of , , and of retroviruses. It is unknown through which of the following likely processes the copy was inserted into : endogenization (infection of a germline cell by an exogenous virus), reinfection (infection by a virus produced from a previously endogenized provirus), or retrotransposition (intracellular relocation of a provirus). In any case, the insertion into is considered to have been a recent event on an evolutionary timescale because albino mutant alleles generally do not persist for long because of their deleterious effects in wild circumstances.