Figure 3.—

Phenotypic reversion, event 1. The crossing of two vga-9/S73A-neo compound heterozygotes led to an extensively pigmented mouse (#1588) that apparently was mosaic for a novel Mitf allele, S73A¹-neo, and that gave rise to phenotypically and genotypically different offspring. Using the indicated breeding scheme, a mouse (#1822) homozygous for S73A¹-neo, was generated. Genomic Southern hybridization as described in Figure 1 indicated that this mouse lost the extraneous wild-type band but retained the targeted recombinant band.