Chocolate Labradors will have a genotype with at least one dominant E allele, but must have only recessive b alleles: bbEE and bbEe. Yellow Labradors with black skin pigment will have a dominant B allele but must have recessive e alleles: BBee or Bbee. These represent recessive mutations in the TYRP1 gene, and since mammals have two copies of each gene, one from each parent, an animal with at least one copy of the fully functioning TYRP1 protein (represented as 'B') will display the dominant trait, black pigmentation, while to display brown pigmentation, both copies of this gene must be mutant alleles (collectively represented as 'b'). The interplay between these two genes determines the colour of a Labrador Retriever, and is widely used as an example of epistasis. These genes assort independently, so a single genetic cross involving two black Labradors each with a recessive allele at both the B and the E locus (BbEe) has the potential of producing all of the possible colour combinations, while crosses involving chocolate dogs can never produce black (there being no dominant B allele in either parent) but can give rise to yellow.

The two chemicals stimulate the nervous system and elevate the heart rate. Dogs are too sensitive to these chemicals … Dogs that carry at least one D will not have a diluted coat. Black Labradors can have any genotype with at least one dominant allele at both the B and E loci: BBEE, BBEe, BbEE, or BbEe. If a dog possesses the dominant phenotype for the extension allele (genotype EE or Ee), then it will display the fur colouration determined by its brown locus genotype, while a dog with the recessive extension trait (ee) will have a yellow coat with either black (BB, Bb) or brown (bb) exposed skin. Those affecting the colour of the dark pigment, eumelanin, are referred to as the B (brown) locus. Thus a dog with the genotypes BB or Bb will express black eumelanin, while brown eumelanin will be seen in dogs with the bb genotype. If two dogs carrying the Dd genotype are bred, diluted offspring could be produced.

In most dogs, activity of MC1R is modulated by two signaling molecules, a repressor that is a product of the Agouti gene (A locus), and an activator, β-Defensin 103 (CBD103), recently named the K locus. The ability of the E locus to override the coat colour directed by the B locus is a classical example of epistasis, where multiple genetic loci affect the same observed trait. It also acts as a diuretic and muscle relaxant and can be used medically, but because our pooches can’t metabolize theobromine in the same way as humans, they are much more sensitive. White chocolate poses a very low risk of chocolate poisoning, with only 0.25 mg of theobromine per ounce. Depending on your dog’s blood theobromine levels at their peak, the effects of chocolate toxicity resolve within one to four days. The good news is that taking care of your dog’s teeth is not difficult or time-consuming. The good news though, vomiting and increased urination are good symptoms to have because this helps dogs get rid of the toxins quickly. While chocolate is a popular ingredient in many of the foods we love, it’s NOT good for dogs.

A variant of the functional MC1R allele that produces a facial 'mask' in other breeds of dogs (Em) is also present in Labradors, but since the colour of the mask is determined by the B locus, in Labradors the mask this gene produces is indistinguishable from the overall coat colour. With their characteristic intelligence, obedience, my cat licked roach poison and eagerness to please, Labradors excel at a variety of dog sports. Your veterinarian will induce emesis if your dog ate cocoa powder recently. During treatment, your veterinarian will monitor the dog's kidney function levels daily to assess the response to treatment and determine whether the treatment needs to become more aggressive. 2. Call your veterinarian: Contact your veterinarian or an emergency veterinary clinic right away. But before giving your dog foods that you crave, read on and learn which foods are safe, and which can send your dog straight to the emergency vet. It actually does the same for us, but we can metabolize it quickly enough to prevent any danger. That means that same 80-pound Lab would be at a toxic dose after only 3.5 ounces!