The Basics:
* Merle gene: This gene is responsible for the "merle" pattern, characterized by patches of diluted color. In Border Collies, the merle gene dilutes black to blue, creating the classic black and white pattern.
* Agouti gene: This gene determines the distribution of pigments on the coat. It can create different patterns like solid black, tan, or even a "saddle" pattern.
* White spotting gene: This gene determines the extent of white markings. It can lead to a wide range of white patterns, from small patches to large areas of white.
How it works together:
1. Merle gene: A Border Collie with the merle gene will have areas of black diluted to blue, creating the black and white patches.
2. Agouti gene: This gene can modify the merle pattern further, sometimes leading to tan patches or a "saddle" pattern within the merle areas.
3. White spotting gene: This gene contributes to the amount of white markings, adding more white patches to the black and blue merle pattern.
The result:
The combination of these genes creates the unique and diverse coat patterns seen in Border Collies. Some dogs may have large areas of white, while others may have just a few small patches. The exact pattern is determined by the specific combination of genes inherited from both parents.
Important note:
It's important to remember that breeding merle dogs can have serious health consequences. Double merle dogs (those inheriting the merle gene from both parents) are at risk for a range of genetic health issues, including blindness and deafness. Responsible breeders carefully screen their dogs and avoid breeding merle to merle.