Figure 2. Confirmation of the rd1 genotype of FVB/N and C3H/HeOu mice. A: Presence of the provirus insertion in intron 1 of the PDE6B gene tested with Giménez and Montoliu’s three-primer method [54]. The primer pair RD3/RD4 amplifies a 550 bp product only in rd1 lines, whereas the primer pair RD3/RD6 amplifies a 400 bp product only in Pde6b⁺ control mice. B: The nonsense mutation in codon 347 of rd1 creates a DdeI restriction site. Digestion of a 300 bp PCR product spanning the mutation site with DdeI yielded two diagnostic fragments of 106 bp and 139 bp in both rd1 strains. Control: uncut 300 bp PCR product. C: DNA sequencing over Tyr347 (underlined) confirms the C→A mutation (*) introducing a stop codon (TAA) in both rd1 strains.