In this study, we found that a ratio of 1∶2 of wild-type vs. mutant protein is enough to significantly reduce the retinal degeneration caused by the truncated Rp1 protein, as evidenced by the relative preservation of retinal function and structure in the 12-month-old Rp1Q662X/Q662X : N-SF-TAP-Rp1 mice compared to the Rp1Q662X/Q662X mice. This evidence concerns the gene RP1 and retinal degeneration.