The Color Genetics of Labradors

This blog post is designed to help breeders, pet owners, and Labrador enthusiasts understand the genetics behind the three recognized Labrador colors: black, chocolate, and yellow. We’ll explore how genes are inherited from parents to offspring, the role of dominant and recessive traits in coat color, and the unique effect of recessive epistasis in Labradors. Finally, we’ll explore the genetics behind so-called “Dudley” Labradors and dilute-colored Labradors.

How Are Genes Inherited from Parents to Offspring?

Each of our genes is made up of a pair of alleles—different versions of the same gene that determine specific traits in an organism. Offspring inherit one allele from each parent, meaning they receive one from the mother and one from the father. Which allele they inherit from each parent is entirely random, with a 50% probability of inheriting either one. The combination of the two alleles is defined as a genotype, and each allele is represented by a letter.

The Role of Dominant And Recessive Traits in Labrador Coat Color

A black Labrador can have the following genotypes: BBEE, BbEE, BBEe and BbEe.

Labradors have two genes that control coat color; one gene which controls Black vs. Chocolate coloring (the B locus), and one gene which controls the yellow masking effect (the E locus). Let’s take a look at the B locus:

The B locus controls the black or chocolate coloring. Looking at the gene name, you can already guess what letters we use to represent the two alleles in this gene:

• The allele coding for the black color is represented by a “B”

• The allele coding for the chocolate color is represented by a “b”

A chocolate Labrador can have the following genotypes: bbEE and bbEe.

The B allele is dominant; this means, that a dog only needs one of these alleles to express the black coat color. Meanwhile, the b allele is recessive; this means that a dog needs two of these alleles to express the chocolate coat color. Let’s take a look at the possible allele combinations a dog can have in the B locus:

• BB = The dog has a black coat, as it has two B alleles that code for the black color.

• Bb = As the B allele dominates over the recessive b allele, the dog has a black coat, but it carries chocolate, meaning an offspring can inherit the b allele. If you breed this dog to a chocolate dog or a black dog carrying chocolate, you have a chance of getting chocolate puppies.

• bb = The dog has a chocolate coat, as it has two recessive b alleles that code for the chocolate color.

The Role of Recessive Epistasis in Labradors

Now it gets exciting! So far we’ve described the black and chocolate alleles, but not the yellow. This is because a yellow coat is determined by a different gene, the E locus.

The E locus codes for specific receptors in the pigment-producing cells. To produce black or chocolate pigment, these receptors have to be present. If not, these colors can not be produced, and the dog will be yellow; yellow is actually a Labrador’s “default pigment”.

The letters we use to represent the alleles in this E locus are;

A yellow Labrador can have the following genotypes: BBee, Bbee and bbee.

• The dominant allele “E”

• The recessive allele “e”

The E locus gene exhibits recessive epistasis, meaning it can override the expression of another gene. Epistasis occurs when one gene masks or modifies the effect of another, and in this case, the E locus controls whether the B locus (black vs. chocolate) is expressed at all. With recessive epistasis, the gene must have two recessive alleles (in this case "ee") to override the B locus.

Lets take a look at the possible combinations of alleles in the E locus:

• EE = the dog has two dominant E alleles, and it is therefore the B locus which determines coat color, that is to say, that the dog is either black or chocolate.

• Ee = the dog has one dominant E allele, and one recessive e allele; this means, that the B locus will determine coat color, and the dog is either black or chocolate.

• ee = the dog has two recessive e alleles, and the E locus will therefore mask the effect of the B locus. No matter the allele combination in the B locus, the dog will be yellow.

General Rules for Labrador Coloring in Breeding

For two Labradors of the same color to produce puppies of a different color (e.g., two black dogs producing a yellow puppy), both must carry the recessive gene for that color. The only exception is black—if at least one parent is black, they can produce black puppies regardless of whether the other dog carries the black allele.

Two black Labradors can produce puppies of all three colors—black, chocolate, and yellow—depending on the alleles they carry.

Two chocolate Labradors can never produce black puppies but may produce both chocolate and yellow puppies if they both carry the yellow allele “e”.

Two yellow Labradors can only produce yellow puppies, regardless of whether they carry black or chocolate.

What Is A “Dudley” Labrador?

A Dudley Labrador is a yellow Labrador with the genotype bbee, which results in a lack of black pigment on the nose, muzzle, and eye rims. Instead, these areas appear pink or brownish at birth, and will stay like that for the rest of the dog’s life. While some refer to any yellow Labrador with a brown nose as a Dudley, others insist that a true Dudley must have a completely pink nose. Regardless, these dogs lack the black pigmentation that is highly desired in yellow Labradors. Because of this, Dudley Labradors are generally considered undesirable by most breeders and are disqualified from the show ring

The Dilute Gene in Labradors

Labradors have only three recognized coat colors: black, chocolate, and yellow (which ranges from nearly white to deep fox-red). Any other coat color is disqualified in the show ring. However, an increasing number of breeders are producing so-called “silver,” “charcoal,” and “champagne” Labradors—colors determined by the dilute gene, located at the D locus.

• The dominant allele at the D locus is represented by “D”, which results in a standard, full-color coat.

• The recessive allele is represented by “d”. A dog must inherit two copies (dd) to have a diluted coat color.

In Labradors:

A chocolate Labrador with the dd genotype appears silver.

A black Labrador with the dd genotype appears charcoal.

A yellow Labrador with the dd genotype appears champagne.

Much controversy have arisen around the subject of diluted Labradors. Breeders of these dogs insist that the dilute genotype “dd” occurs naturally in Labradors, and the first silver Labradors were the product of breeding two dilute carriers together. Others believe that the dilute coloring is a product of crossbreeding with Weimeraners, a breed who naturally carries the dilute gene.

Regardless of their origins, many Labrador breeders take great care to ensure their dogs do not carry the dilute gene by testing for it. This is partly due to concerns about Color Dilution Alopecia (CDA)—a genetic condition associated with the dd genotype. CDA can cause chronic hair loss, skin lesions, and irritation, making it a serious welfare issue for affected dogs.