The colour of a Labrador's coat is determined by genetics, just like almost all of the traits that offspring get from their parents. The three basic colours of a Labrador are black, chocolate (brown) and yellow, with a wide range of shades of yellow, from palest cream to fox red. The colour of a Labrador's coat is determined by the interplay of several distinct genes, which direct the production and expression of two pigments, eumelanin (brown or black pigment) and pheomelanin (yellow to red pigment). The B locus is home to a pair of genes called B genes, which determine whether a Labrador will be black or brown. One of the pair comes from the mother, and the other from the father. There are two types of B gene: big B, which contains an instruction to make lots of eumelanin and causes a black Labrador coat, and little b, which contains an instruction for less eumelanin and causes a brown or chocolate coat. Big B is a dominant gene, and little b is a recessive gene. The E locus is home to the E genes, which determine whether a Labrador will be black or chocolate, or yellow. The big E gene is dominant and does not interfere with the B genes, while the little e gene is recessive and masks the B genes, resulting in a yellow coat.
Characteristics | Values |
---|---|
Number of coat colours | 3: black, chocolate, and yellow |
Genes involved | 2: B genes and E genes |
B genes | Big B (dominant) and little b (recessive) |
E genes | Big E (dominant) and little e (recessive) |
Dilute genes | D genes: big D (dominant) and little d (recessive) |
What You'll Learn
The role of the 'bee' genes
The dominance of the 'big B' gene means that even if a Labrador inherits one 'big B' and one 'little b' gene, the resulting coat will be black. This is because the 'big B' gene overrides the 'little b' gene. For a brown coat to be produced, there must be no 'big B' gene present, so the Labrador must inherit two 'little b' genes, one from each parent.
The 'bee' genes interact with other genes, such as the 'eee' genes, to determine the final coat colour. The 'eee' genes can, in some cases, switch off the 'bee' genes, resulting in a yellow coat. The 'eee' genes also have two types: 'big E' and 'little e'. The 'big E' gene does not interfere with the 'bee' genes, while the 'little e' gene can mask or switch them off, resulting in a yellow coat.
The interplay between the 'bee' and 'eee' genes, along with other genes, determines the three recognised colours of Labrador Retrievers: black, chocolate, and yellow. The complexity of these genetic interactions means that predicting the colour of Labrador puppies can be challenging without knowing the parents' genotypes.
Why Cats' Coats Fluff Up
You may want to see also
The role of the 'eee' genes
The colour of a Labrador Retriever's coat is determined by the interplay of several distinct genes. The genes responsible for the pigments eumelanin (brown or black) and pheomelanin (yellow to red) are the most important in determining the colour of a dog's coat.
The role of the eee genes:
The 'eee' genes, also known as the E locus, play a significant role in determining the colour of a Labrador's coat. The E locus creates the black facial mask seen in many dogs, as well as yellow or red coats. The E locus is responsible for the expression of pheomelanin, the pigment that gives red and yellow pigmentation. The effects of pheomelanin are only visible if there is no eumelanin expressed in the fur, as the dark eumelanin will mask any pheomelanin present. This is why yellow Labradors can range in colour from light cream to copper-red.
The E locus has four alleles, which are Em (melanistic or dark mask), Eg (grizzle), E (black), and e (red). The E locus has a hierarchical dominance pattern, with Em being dominant over the other E alleles. The E allele allows the dog to produce eumelanin in its coat and is dominant over the e allele (recessive red). Dogs with the EE or Ee genotype can produce dark hairs (black, brown, blue, or isabella), but their distribution will depend on the genotypes at the K and A loci.
Dogs with the ee genotype (recessive red) will not produce any dark hairs, regardless of their genotype at the K, A, B, and D loci. The shade of red in their coats can range from deep copper to yellow to white. This variation in red colour intensity is controlled by multiple genetic loci and has different genetic determinants in different breeds.
The E locus also determines whether the phenotype due to the third genetic locus affecting coat colour will be evident. In other words, the E locus can override the coat colour directed by the B locus, which is a classical example of epistasis, where multiple genetic loci affect the same observed trait.
In summary, the eee genes play a crucial role in determining the colour of a Labrador's coat by influencing the production of pheomelanin and interacting with other loci to determine the final coat colour.
Frock Coats: A Historical Overview
You may want to see also
The role of the 'TYRP1' gene
The colour of a Labrador Retriever's coat is determined by the interplay of several distinct genes. The gene that determines whether a Labrador will be black or brown is Tyrosinase-related protein 1, or TYRP1 for short. This gene is different from the one that determines yellow coat colour.
There are four known alleles at the TYRP1 gene in the Labrador Retriever: one is the allele for black (designated as B) and three different alleles that result in chocolate (collectively designated as b). The black coat colour (B) is dominant to the chocolate (b). Therefore, a puppy will only be chocolate brown if each parent contributes a chocolate allele (bb). If one or both parents contribute the dominant black allele (BB or Bb), the puppy will be black (BB or Bb).
In dogs, three mutations in the TYRP1 gene have been identified, one resulting in a truncation of the protein, and the other two leading to an amino acid deletion or a single amino acid substitution in the sequence of the protein. All of these mutations are found across the range of dogs and are thought to have preceded the divergence of distinct breeds. Each of the mutations appears to eliminate or significantly reduce enzymatic activity, and the colouration phenotypes (the visible traits) produced by the three mutations are indistinguishable.
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 (BB or Bb) will display the dominant trait, black pigmentation. To display brown pigmentation, both copies of this gene must be mutant alleles (bb). 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.
Navy Sport Coat: Black Pants Match?
You may want to see also
The role of the 'MC1R' gene
The colour of a Labrador Retriever's coat is determined by the interplay of several distinct genes. One of these genes is the melanocortin 1 receptor gene, or MC1R for short. This gene plays a role in the production of eumelanin, which is the pigment responsible for brown or black colouration.
The MC1R gene encodes the melanocortin 1 receptor, which binds to melanocyte-stimulating hormone (α-MSH). This interaction induces the synthesis of eumelanin. The MC1R gene has been found to play a role in determining coat colour in a variety of species, including humans, pigs, mice, dogs, and cattle.
In Labradors, the MC1R gene is responsible for determining whether a dog's coat will be yellow. An e allele at the MC1R gene prevents the expression of the black or chocolate colour in the hair follicle, resulting in a yellow coat. For a Labrador to be yellow, it must have two recessive alleles of the MC1R gene (ee). This means that both parents must contribute a yellow allele (e). If only one or no yellow-causing alleles are contributed, the puppy will be either black or chocolate, depending on the alleles present at the TYRP1 gene.
The role of the MC1R gene in determining coat colour is not limited to Labradors. In a study of Central European cattle breeds, the MC1R gene was found to play a significant role in coat colour determination. The ED allele was characteristic of white-backed cattle breeds, while the red breeds had a dominant E+ allele. The SP breed, on the other hand, had a recessive e allele, resulting in a separate clade in the phylogenetic tree.
In Chinese sheep, mutations in the MC1R gene have been linked to black coat colour. Two non-synonymous mutations (c.218 T>A and c.361 G>A) and three synonymous mutations (c.429 C>T, c.600 T>G, and c.735 C>T) were identified in the MC1R gene. These mutations were associated with black coat colour in the Minxian Black-fur sheep breed.
The MC1R gene is an important determinant of coat colour in a variety of species, including Labradors. Its role in pigmentation has provided valuable insights into the biology of coat colour variation and the evolution of domesticated animals.
Buttoning Your Sport Coat: Which Button?
You may want to see also
The role of the 'Dilute' genes
The D locus, or 'dilute' gene, is responsible for the colour variation observed in Labradors. This recessive gene, also known as the dilution (D) locus, can dilute the standard colour genotypes of Labradors if the dog carries two copies of the recessive dilute allele, dd. The standard colours recognised by the American Kennel Club (AKC) are black, yellow, and chocolate.
The 'dilute' gene affects the colour of the pigments eumelanin and pheomelanin. In black Labradors, the D locus gives a softer, charcoal coat colour. In yellow Labradors, it results in a paler 'champagne' yellow. In brown Labradors, the gene dilutes the coat colour to a striking silver, which has caused some controversy among Labrador enthusiasts.
The dilution factor was not originally part of the genetics of Labrador Retrievers, and it is linked to a skin disease called Colour Dilution Alopecia. The gene responsible for this colour variation in all dog breeds is the recessive 'dilution' (D) locus, and studies have linked the diluted trait to a mutation in the melanophilin (MLPH) gene.
The diluted trait can arise through inbreeding to select for other traits, undisclosed outbreeding with other breeds, or spontaneous mutation. The standard for Labrador Retrievers does not include dilution colours, and any dilute is considered a breed disqualification. However, the AKC will register purebred Labs that are dilute in colour under the colours of black, yellow, or chocolate.
Coat of Sweetness
You may want to see also
Frequently asked questions
The three main Labrador colors are black, chocolate, and yellow. However, there are other colors available, such as charcoal, silver, and champagne.
The coat colors in Labradors are determined genetically. The interplay among several distinct genes affects the production and expression of two pigments, eumelanin (brown or black pigment) and pheomelanin (yellow to red pigment).
Genetic tests are available to determine the genotype of your dog and predict the color of your puppies. However, it can be difficult to predict the color of Labrador puppies without knowing the parents' genotypes.