Mosaics and Other "mis-marks"
Sponenberg and Bigelow published their findings in the Journal of Heredity on a mosaic male Labrador Retriever who exhibited random, but distinct black and yellow patches throughout his coat. He was the result of a black female (carrying yellow) bred to a yellow male. This dog was mated to 2 yellow females, one black female, and 2 chocolate females. All puppies resulting from these breedings were either black or yellow and the percentages of each in each mating follow the inheritance pattern of a yellow Labrador (BBee) with black pigment. They explained that this pattern was not characteristic of a “merle” coat because merle develops from a transposable element and because all of the mosaic dog’s puppies did not exhibit mosaic colouring, but were normal black or yellow, therefore there is no evidence of a transposable element. Sponenberg acknowledges the likelihood of a recessive gene causing this mosaic pattern, but says it would be unique and is highly unlikely. The most probable cause was a somatic mutation early in development. (1987)
Other “mis-marks” such as brindling, tan points, white spots, and rings around the tails are common in Labradors. Each of these conditions have various underlying genetic as well as environmental causes. Examples of “mis-marked” Labradors can be found at .
Read more about this topic: Labrador Retriever Coat Colour Genetics