Enter a genotype (for example, BB, Bb, or bb) into the calculator to determine the expected coat color for a simple single-gene dominant/recessive model (where B is dominant for black and b is recessive for brown). Real coat color genetics vary by species and often involve multiple genes.
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Coat Color Rule (Simple Dominant/Recessive Model)
The following rule is used to predict coat color from genotype in a simple single-gene model (B = black, b = brown):
\text{Coat Color}=
\begin{cases}
\text{Black}, & \text{if genotype is } BB \text{ or } Bb \\
\text{Brown}, & \text{if genotype is } bb
\end{cases}Variables:
- Genotype is the two-allele combination at the B/b locus (BB, Bb, or bb)
- B is the dominant allele associated with black coat color in this simplified example
- b is the recessive allele associated with brown coat color in this simplified example
To determine the expected coat color in this simplified model, check whether the genotype contains at least one dominant B allele (black). Only bb produces brown.
What is a Coat Color?
Coat color refers to the visible color (and often the pattern) of an animal’s fur or hair. Coat color is primarily determined by genetics: multiple genes can affect pigment type, pigment distribution, and patterns (for example, whether pigment is primarily eumelanin vs. pheomelanin, and whether the coat is solid, spotted, striped, etc.). Environmental factors such as age, sun exposure, and health can affect how a coat looks (for example, graying with age or sun-bleaching), but they do not change the animal’s underlying genotype. In some species, specific coat-color-related genes can be linked to health conditions.
How to Calculate Coat Color?
The following steps outline how to determine the coat color from genotype in the simplified B/b model used by this calculator:
- Identify the two alleles in the genotype (each allele must be B or b).
- If the genotype includes at least one B allele (BB or Bb), the expected coat color is black (dominant trait expressed).
- If the genotype is bb, the expected coat color is brown (recessive trait expressed).
- Keep in mind that many real-world coat colors/patterns require multi-gene models, so this result is only for this simplified teaching example.
Example Problem:
Use the following variables as an example problem to test your knowledge.
Genotype: Bb
Expected coat color: black
