An extension locus mosaic Labrador retriever dog

A mosaic male Labrador retriever with coat color of black and yellow areas is described. Matings of this dog to black, chocolate, and yellow Labrador bitches were consistent with his producing only yellow (e) gametes at the extension locus. His phenotype could have resulted either from somatic mutation of E to e or e to E early in development; or from fusion of Ee and an ee male zygotes to form a chimera.