Importantly, mice with the genotype Mertk+/+;Tyro3129/129 exhibit a TYRO3 level comparable to that of Mertk-/-;Tyro3129/129 mice, demonstrating that lower expression is a property of the Tyro3129 allele and not secondary to retinal degeneration. The gene discussed is MERTK; the disease is retinal degeneration.