These anomalies occur only with the
dominant white gene, and even some cats with that dominant gene are exceptions if they are born with even small patches of color other than white.
Unlike the Black German Shepherd, however, whose true color is solid black, the
recessive white gene acts as a mask, blocking the dog's true color and pattern and causing it to appear white.
With so few northern whites remaining, it was decided that a southern white male would be introduced to Fatu and Najin in the hope of producing offspring that would at least preserve some of the
northern white genes.
Although the «white» version of the gene is recessive, black bears with one
white gene and one black are uncommon.
If the Blenheim is being bred to a Black & Tan that does carry
the white gene then all four colors are possible and some white mismarking is possible on the whole colors.
When a Blenheim is being bred to a Ruby with
the white gene then both Ruby and Blenheim colored puppies are possible and some white mismarking on the Ruby colored puppies is possible.
When you breed a Blenheim to a whole color (black / tan or ruby) the offspring will automatically carry
the white gene giving the whole color offspring the ability to produce all 4 colors if bred to a Blenheim or tri color or if bred to another whole color that carries the white gene as well.
Whan a Blenheim is being bred to a Black & Tan that does not carry
the white gene then both whole colors are possible and some white mismarking is possible.
When a Blenheim is being bred to a Ruby which does not carry
the white gene all the puppies will be ruby and some white mismarking is possible.
There are many breeders who refuse to admit that there is even
a white gene existing in the Yorkies.
NO WHITE GENES allowed on property...
As puppy mills commonly trade breeding stock back and forth, the gene is introduced into other mills (in exchange with Fox Terrier or Poodle infused particolors, etc.) and so
the white gene becomes firmly established in that population.
Though
the white gene doesn't trace back to a clear record, it's presumed to be recessive and independent of any other genes.
The white gene is not a dilute gene, like liver and blue; it is a masking gene (meaning the recessive gene masks the dog's true color).
Some people think that if you breed a White German Shepherd with a standard one,
the white gene will cause the puppies to be born a lighter color.
If the non-white carries the recessive
white gene, the puppies will have a 50/50 chance of being white or colored.