Have you ever wondered how it is possible that, when crossing two solid black dogs, a brown or tan puppy suddenly appears in the litter?
A dog's coat colour is not random. It is a complex genetic code, made up of "switches" called Locus (plural: Loci), which interact with each other to paint the final canvas that we see in the phenotype.
The alphabet of colour: Understanding the Loci
A Locus is, basically, the postal address of a gene on the chromosome. In the world of canine colour, there are four key players that dictate almost everything you see: Agouti (A), K, E and B.
The key to genetics lies in dominance and recessivity. Some genes are "bossy" and hide others, whilst recessive genes remain in the shadows, waiting for the exact moment, the right combination, to manifest themselves in a new generation.
Locus E and Locus B
To understand why that brown puppy appeared in a litter of black parents, we must first look at these two switches:
- Locus E (Extension): This is the master switch. It decides whether the dog can produce dark pigment (eumelanin) in its coat. If the dog is recessive (ee), the dark pigment is blocked, resulting in red or yellow dogs, regardless of what other genes may dictate.
- Locus B (Black/Brown): If Locus E allows for dark pigment, Locus B decides its tone. The dominant gene (B) dictates black, whilst the recessive gene (b) dictates brown (also known as chocolate or liver).
Locus K and Agouti (A): The canvas and the artist
If the dark pigment is activated (E) and is black (B), the masters of design come into play:
- The power of the Locus K: This is the great "eraser". If the dog possesses the dominant gene (KB), it will become solid black, hiding any other pattern. It is like a coat of paint covering the canvas completely.
- The artist Agouti (A): If Locus K is not dominant (that is, the dog is kyky), the Agouti gene takes control. This gene distributes colour in intricate patterns:
- Sable: The wolf pattern.
- Fawn: Mainly red or yellow with dark tips.
- Black and tan: The classic pattern of the Doberman or Rottweiler.
- Solid black: Completely black.
Understanding layer genetics is fascinating, but trying to predict it through trial and error is risky and inefficient. At Koko Genetics, we specifically analyse these switches. Our DNA test for dogs not only tells you what colour your dog is, but what colours it is hiding in its genetic code, allowing breeders to predict the characteristics of their future litters.
