White Shepherd - Genetics

Genetics

There are many misconceptions about white-coat German Shepherd Dogs and the gene that expresses for their coat color. Clarence C. Little's The Inheritance of Coat Color in Dogs hypothesized that dilution or partial albinism ce, ca and cch alleles of the so-called (C) gene caused the cream and white coat color variants in domestic dogs. Little's hypothesized partial albinism explanation for cream and white colored coats has been applied across most domestic dog breeds, including white coat dogs from German Shepherd breed lines, since Little first published his book.

However, comparative analysis of the dog genome and specific breed DNA sequences now shows that Little's hypothesized gene (C) color dilution explanation for cream and white colored coats is most likely not a relevant determinant of cream and white coats known to commonly occur in many dog breeds. Little's 1957-era partial albinism dilution explanation, as applied to explain domestic dog white and cream coat colors, can be replaced by the findings of modern genetic research.

Research has shown that a recessive e allele at the Extension (E) gene is at least partially responsible for cream and white coat color. The (E) gene, now identified as the Melanocortin 1 receptor (MC1R) gene, is one of the two genes known to code for alleles that are absolutely fundamental to the formation of all German Shepherd Dog colored coat variations. When the recessive allele is inherited from each breeding pair parent, the e/e genotype offspring of certain breeds, including white coat dogs from German Shepherd breed lines, always have cream or white colored coats.

White Shepherds were once blamed for color dilution or paling for the entire breed because the recessive e allele of the MC1R (E) gene locus masks expression of alleles at other gene loci that actually do code for lighter (often termed as diluted or pale) colors of silver, black and tan or liver. German breeders of the 1920s and 1930s misinterpreted pale-colored offspring of white dogs as an undesirable "white" genetic trait. A homozygous dog of normal color paired with a white GSD always produces full colored puppies because the e allele is recessive.