Mouse Coat Color Calculator
Set each parent's genotype at the agouti, black, albino, dilute, and pink-eyed loci and see the expected coat colors of the litter.
Try Moustra freeHow mouse coat color genetics works
Mouse coat color is determined by a set of interacting Mendelian gene loci. Each locus has a dominant and a recessive allele; the combination of alleles across all loci — together with epistatic interactions — produces the final visible phenotype. This calculator models the five classical loci:
| Locus | Dominant allele | Recessive allele |
|---|---|---|
| Agouti (A) | AA — Agouti (banded) | aa — Non-agouti (solid/self) |
| Brown (B) | BB — Black | bb — Brown / chocolate |
| Albino (C) | CC — Full colour | cc — Albino (white) |
| Dilute (D) | DD — Dense pigment | dd — Dilute (blue/lilac) |
| Pink-eyed (P) | PP — Normal eyes | pp — Pink-eyed dilution |
The albino locus (C) is epistatic to all other pigment loci: a mouse that is homozygous recessive (cc) cannot produce any pigment, appearing white with red eyes regardless of its A, B, D, or P genotype. Similarly, the dilute (D) and pink-eyed (P) loci both reduce pigment intensity but through distinct mechanisms — dilute affects pigment granule distribution (producing blue or lilac coats), while pink-eyed dilution additionally affects eye color.
How to use this calculator
- Set Parent 1's genotype — for each of the five loci, choose whether the parent is homozygous dominant, heterozygous, or homozygous recessive. The genotype string (e.g. AaBbCCDDPP) updates live below the selects.
- Set Parent 2's genotype — repeat for the second parent. You can model any combination: purebred × carrier, two carriers, outcross, and so on.
- Read the distribution table — the calculator enumerates all 2⁵ possible offspring genotype combinations, applies epistasis rules, and groups the results by phenotype. Each row shows the expected percentage of pups with that coat color.
- Share or export — use the Share URL button to copy a link that encodes both parent genotypes, or export the distribution as a CSV file.
- Track in Moustra — for ongoing colony management, record individual animal genotypes, track coat-color inheritance across generations, and plan future crosses directly in Moustra.
Frequently Asked Questions
What determines mouse coat color?
Mouse coat color is controlled by multiple interacting gene loci. The five most important classical loci are: A (agouti), B (brown), C (albino), D (dilute), and P (pink-eyed dilution). The combination of dominant and recessive alleles at each locus — plus epistatic interactions — determines the final coat color phenotype.
What is epistasis and why does albino hide all other coat colors?
Epistasis occurs when one gene masks the expression of another. The albino locus (C) is epistatic to all pigment-producing loci: a mouse that is homozygous recessive at C (cc) cannot produce any pigment at all, so it appears white with red eyes regardless of its genotype at A, B, D, or P. This is why two non-albino carriers (Cc × Cc) can produce 25% albino offspring.
What do the A, B, C, D, and P loci control?
A (agouti) controls whether hairs are banded (agouti pattern) or solid. B (brown) determines black vs. brown/chocolate eumelanin. C (albino) controls whether any pigment is made at all — cc is epistatic white. D (dilute) reduces pigment clumping, turning black into blue and brown into lilac. P (pink-eyed dilution) causes further pigment dilution with pink/ruby eyes independent of the D locus.
What is the difference between dilute (D) and pink-eyed dilution (P)?
Both loci dilute coat color, but through different mechanisms and with different eye effects. Dilute (dd) affects pigment granule distribution, producing blue (from black) or lilac (from brown) coats with normal dark eyes. Pink-eyed dilution (pp) reduces pigment in the coat and causes pink or ruby-colored eyes. The two can act together for additional dilution.
Is this coat color calculator accurate for my mouse line?
This calculator models the five classical Mendelian loci (A, B, C, D, P) with simple dominance and epistasis. It accurately predicts expected litter ratios for standard laboratory and fancy-mouse crosses. However, it does not account for modifier genes, incomplete penetrance, or less common loci found in specialized strains. For maintaining detailed genotype records for your colony, use Moustra.
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