|Athro, Limited Biology Genetics Sheltie Coats|
|Sheltie Coat Color Inheritance|
Sheltie (Shetland Sheepdog) puppies look like their parents, but not exactly. Sheltie puppies inherit characteristics from their parents. Individuals have an appearance (say a Sheltie with a Golden Sable coat). Individuals also have genes. Each Sheltie carries two copies of each gene, one from each parent. A gene often comes in two or more flavors (such as a gene for the extent of white in the coat that can make the coat mostly white, give large white patches in the coat, or produce the typical Sheltie white bib, neck, feet, and tip of tail). A Sheltie can thus have two copies of the gene with the same flavor (sable-sable), or two copies of different flavors (sable-bicolor). Sheltie Coat color is controlled by more than five genes, three of which are probably the most important.
Let's pretend that two genes explain the inheritance of Sheltie coat color (this ignores several complications such as variability in the extent of dark fur shading in Pure for Sable and Trifactored Sable Shelties). These two genes modeled in this calculator are 1) the gene for sable coat (with alleles for Sable , Tricolor [Black with tan points], and Bicolor [black without tan points]), and 2) the merling gene. This ignores the a number of complexities. We can ask what the coat colors would be expected in Sheltie puppies produced by different combinations of parents. For example, what happens when Trifactored Sable and Blue Merle Sheltie parents have a litter of puppies?
All making sense? Can you figure out the genotype of a Sheltie from its coat color?
Dogs, including Shelties, have several coat color genes. Two of these genes are named Agouti and Merle. These are the genes used in this calculator. You can use a Punnett Square to work out the crosses, and figure out what offspring the breeding of a particular Sheltie might produce.
Ignoring the extent of white in the coat, this calculator presents the standard hypothesis for the genetics of the most important coat colors in the Sheltie. This hypothesis is that one gene (the Agouti gene) has three alleles (Sable, Tricolor, Bicolor) and that this single gene controls both whether a Sheltie is sable or black, and whether it has tan points (Tricolors having a black coat with tan points). An alternate hypothesis is that two separate genes are involved. Under this alternate hypothesis, one gene (the Agouti gene) produces sable or black coat colors, while the other gene can produce tan points on black coats. Breeders have conflicting opinions about these hypotheses. We favor the hypothesis of a separate gene for tan points, but present the three alleles of Agouti here for simplicity.
Another complication we ignore in this calculator is the extent of dark fur shading a sable coat. This trait is highly variable, and it is often unclear whether an individual with a shaded sable phenotype has a Pure for Sable or Bifactored or Trifactored Sable genotype.
For more details, see: Sheltie Coat Color Genes