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An extension locus mosaic Labrador retriever dog
1Department of Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg 24061.
The Journal of Heredity
|November 1, 1987
Summary
A mosaic male Labrador retriever displayed unusual coat colors. Genetic analysis suggested the mosaicism resulted from either somatic mutation or zygote fusion, impacting pigment gene expression.
Area of Science:
- Canine genetics
- Coat color genetics
- Developmental genetics
Background:
- Mosaicism in mammals can arise from somatic mutations or fusion events.
- Coat color in Labrador retrievers is determined by multiple genes, including the extension locus (E).
- The extension locus controls the production of eumelanin (black/brown pigment).
Purpose of the Study:
- To investigate the genetic basis of coat color mosaicism in a male Labrador retriever.
- To determine the gametes produced by the mosaic male.
- To elucidate the developmental origin of the observed mosaic phenotype.
Main Methods:
- Phenotypic description of a mosaic male Labrador retriever.
- Pedigree analysis and controlled breeding experiments.
- Segregation analysis of coat color alleles at the extension locus.
Main Results:
- The mosaic male produced only yellow (e) gametes, despite having both black and yellow coat areas.
- Matings with bitches of various coat colors confirmed the production of only yellow gametes.
- This pattern is inconsistent with simple Mendelian inheritance from a non-mosaic individual.
Conclusions:
- The mosaic phenotype likely resulted from either early developmental somatic mutation (E to e or e to E) or fusion of two zygotes (a chimera).
- The observed gamete production suggests the functional alleles present in the germline were exclusively 'e'.
- This case highlights the complex genetic mechanisms underlying mosaicism and its phenotypic expression in dogs.