How color inheritance works
Every dog inherits two copies of each gene — one from the sire, one from the dam. These gene copies are called alleles, and the location on a chromosome where a gene sits is called a locus (plural: loci). For coat color, at least seven major loci work together to determine what color and pattern a dog displays.
Some alleles are dominant — a dog only needs one copy for the trait to show. Others are recessive — the dog needs two copies (one from each parent) for the trait to be visible. A dog carrying one dominant and one recessive allele will look like the dominant form but can pass the recessive allele to offspring. This is why two dogs of the same color can produce puppies of a completely different color.
The standard notation uses uppercase letters for dominant alleles and lowercase for recessive. For example, at the B locus: B (black pigment, dominant) and b (brown pigment, recessive). A dog that is BB or Bb produces black pigment. Only a bb dog produces brown pigment.
The seven major color loci
Each locus controls a different aspect of coat color. Some determine the base pigment, others control whether a pattern shows through, and some modify the intensity of the color. Here is what each one does.
| Locus | Gene name | What it controls | Key alleles | Example phenotypes |
|---|---|---|---|---|
| A (Agouti) | ASIP | Pattern distribution of pigment | Ay (sable), aw (wild), at (tan points), a (recessive black) | Sable German Shepherds, black-and-tan Rottweilers, recessive black Australian Shepherds |
| B (Brown) | TYRP1 | Black vs brown/liver/chocolate base pigment | B (black, dominant), b (brown, recessive) | Chocolate Labradors, liver Springer Spaniels, brown Newfoundlands |
| D (Dilute) | MLPH | Full color vs dilute (lightened) pigment | D (full color, dominant), d (dilute, recessive) | Blue Weimaraners, blue Staffordshire Terriers, isabella Dobermans |
| E (Extension) | MC1R | Allows or blocks red/yellow expression | EM (melanistic mask), E (normal extension), e (recessive red/yellow) | Yellow Labradors (ee), red Golden Retrievers (ee), melanistic mask in Pugs |
| K (Dominant black) | CBD103 | Solid color vs pattern expression | KB (dominant black), kbr (brindle), ky (allows A locus pattern) | Solid black Labrador (KB), brindle Boxer (kbr), patterned dog (ky/ky) |
| M (Merle) | PMEL17 (SILV) | Merle pattern — random dilution patches | M (merle), m (non-merle) | Blue merle Australian Shepherds, merle Great Danes, harlequin patterns |
| S (Spotting) | MITF | White spotting and parti-color patterns | S (solid), sp (piebald/parti), sw (extreme white) | Parti Poodles, piebald Dachshunds, Irish spotting in Collies |
UC Davis VGL, Embark Veterinary, Schmutz & Berryere (2007)
How the loci interact
These loci do not work in isolation — they form a hierarchy. The E locus acts as a master switch: if a dog is ee, it will be red or yellow regardless of what happens at the K, A, or B loci, because the ee genotype prevents dark (eumelanin) pigment from reaching the coat. If the dog has at least one E allele, the K locus takes over: KB produces solid color (overriding the A locus), kbr produces brindle, and ky/ky allows the A locus patterns to show through. The B and D loci then modify the pigment itself — B determines black vs brown, and D determines full strength vs dilute.
Labrador color genetics: a clear example
Labrador Retrievers are the classic example for teaching color genetics because their three colors — black, chocolate, and yellow — are controlled by just two loci: E (Extension) and B (Brown).
- Black: at least one E allele AND at least one B allele (E/- B/-)
- Chocolate: at least one E allele AND two b alleles (E/- bb)
- Yellow: two e alleles, regardless of B locus (ee B/- or ee bb)
This means a yellow Labrador can be genetically "black" (ee BB or ee Bb) or genetically "chocolate" (ee bb) — you can only tell by DNA testing or by the puppies they produce. A yellow Lab with a brown nose is ee bb; a yellow Lab with a black nose is ee B/-.
Punnett square: Bb x Bb cross
When two black Labradors that both carry the chocolate gene (Bb) are bred together, the B locus outcomes follow a simple Punnett square. Assuming both parents are also E/- (carrying at least one E allele), the color predictions for the B locus are:
Expected ratio: 75% black (25% BB + 50% Bb) and 25% chocolate (bb). Two of the three black puppies will carry the hidden chocolate allele.
Merle genetics and the double merle danger
The merle pattern is caused by a SINE insertion in the PMEL17 gene on the M locus. Merle creates random patches of diluted pigment against a full-color base, producing the distinctive blue merle (on a black base) or red merle (on a red/liver base) patterns seen in breeds like Australian Shepherds, Border Collies, and Great Danes.
A merle dog is heterozygous — Mm — carrying one merle allele and one non-merle allele. This is generally safe. The serious danger comes from breeding two merle dogs together.
Double merle
25% chance when breeding merle to merle. Frequently causes microphthalmia (abnormally small eyes), anophthalmia (missing eyes), deafness, or both. Many double merle puppies are born blind and deaf. This is a predictable and preventable welfare issue.
Merle-to-merle breeding
Each puppy has a 25% chance of being double merle (MM), 50% chance of being merle (Mm), and 25% chance of being non-merle (mm). Even in a large litter, the risk of producing affected puppies is unacceptably high.
Merle-to-non-merle breeding
The recommended approach. Each puppy has a 50% chance of being merle (Mm) and 50% chance of being non-merle (mm). No double merle puppies possible.
Cryptic merle
Dogs with shorter SINE insertions may show little or no visible merle but can still produce merle offspring. Must be identified by DNA testing. If bred to a visible merle, can produce double merle puppies.
Color-related health concerns
While most coat colors are cosmetic, some genotypes are associated with specific health issues that breeders should be aware of.
| Color/genotype | Associated condition | Affected breeds | Mechanism |
|---|---|---|---|
| Double merle (MM) | Blindness and deafness | Any merle breed | Disruption of melanocyte development in inner ear and eyes |
| Blue/dilute (dd) | Color Dilution Alopecia (CDA) | Dobermans, Italian Greyhounds, Weimaraners, blue breeds | Abnormal melanin clumping damages hair follicles — causes progressive hair loss |
| Extreme white (sw/sw) | Congenital deafness | Dalmatians, Bull Terriers, white Boxers | Absence of melanocytes in the inner ear (stria vascularis) |
| Recessive red (ee) in some breeds | Generally safe | Golden Retrievers, yellow Labs | No associated health issues — this is a normal, healthy genotype |
Strain (2004), Clark et al. (2006), UC Davis VGL
Breed-specific color genetics
Different breeds use different combinations of loci to produce their characteristic colors. Understanding which loci matter most in your breed helps you predict litter colors and avoid problematic crosses.
| Breed | Key loci | Common colors | Notes for breeders |
|---|---|---|---|
| Labrador Retriever | E, B | Black (E/- B/-), chocolate (E/- bb), yellow (ee) | Yellow can carry chocolate or black — nose color indicates B locus. All Labs are KB/KB at the K locus. |
| Golden Retriever | E | Shades of gold to cream (all ee) | All Goldens are ee — shade variation is due to modifiers, not major loci. No chocolate or black Goldens exist in the breed. |
| German Shepherd | A, E | Sable (Ay), black-and-tan (at/at), bicolor, solid black (a/a) | A locus drives most color variation. Solid black is recessive (a/a). White GSDs are ee but disqualified in most standards. |
| Poodle | A, B, D, E, K, S | Black, brown, cream, apricot, red, blue, silver, parti | One of the most color-diverse breeds. Parti (sp) was historically controversial. Dilute (dd) produces blue and silver. |
| French Bulldog | A, B, D, E, K | Fawn, brindle, cream, blue, chocolate, lilac | Blue (dd) and lilac (bb dd) are popular but associated with CDA risk. Merle is not a traditional breed color and raises health concerns. |
AKC breed standards, UC Davis VGL, Embark breed research
DNA color testing
Visual identification of color genotype is unreliable. Two dogs that look identical can carry very different hidden alleles. DNA testing is the only definitive way to know what color alleles a dog carries and what colors it can produce.
When to test
- Before any breeding — to predict litter colors accurately and avoid undesirable crosses (especially merle-to-merle)
- When a dog's color genotype is ambiguous — sable dogs can carry tan points or recessive black; yellow dogs can carry chocolate
- For breeds with color-linked health concerns — dilute, merle, and extreme white all warrant testing
- When registering puppies — some registries accept DNA color test results as documentation
Major testing providers
| Provider | Test type | Color loci covered | Turnaround |
|---|---|---|---|
| Embark Veterinary | Comprehensive panel (cheek swab) | All 7 major loci + modifiers | 2-4 weeks |
| Wisdom Panel | Comprehensive panel (cheek swab) | All major loci + breed ID | 2-3 weeks |
| UC Davis VGL | Individual locus tests (swab or blood) | A, B, D, E, K, M, S — order individually | 1-2 weeks per test |
Provider websites as of 2025
Embark and Wisdom Panel offer bundled panels that test color alongside health conditions and breed ancestry — often the most cost-effective choice for breeders. UC Davis VGL is useful when you need a specific single-locus result quickly, or when you need a result accepted by a breed club or registry.
Recommended tools
Coat Color Calculator
Predict puppy coat colors from parent genotypes
COI Calculator
Calculate coefficient of inbreeding for planned pairings
Breed Match Quiz
Find the right breed based on your lifestyle and preferences
Sources: Schmutz & Berryere, "Genes affecting coat colour and pattern in domestic dogs: a review," Animal Genetics (2007). Strain, "Deafness prevalence and pigmentation and gender associations in dog breeds at risk," The Veterinary Journal (2004). Clark et al., "Retrotransposon insertion in SILV is responsible for merle patterning of the domestic dog," PNAS (2006). UC Davis Veterinary Genetics Laboratory. Embark Veterinary, Inc. AKC breed standards. This article is for educational purposes and does not replace professional veterinary or genetic counseling.
Coat color genetics FAQs
1How many genes control coat color in dogs?
At least seven major loci (gene locations) are well-characterized: A (Agouti), B (Brown), D (Dilute), E (Extension), K (Dominant black), M (Merle), and S (Spotting). Additional genes influence traits like ticking, greying, and coat texture. Because these loci interact with each other, even a simple two-locus system can produce many different phenotypes.
2What is the difference between genotype and phenotype?
Genotype is the actual genetic makeup — the alleles a dog carries at each locus. Phenotype is what you can see — the visible coat color and pattern. Two dogs that look identical (same phenotype) can carry different hidden recessive alleles (different genotypes), which is why DNA testing matters for predicting litter colors.
3Can two black dogs produce a chocolate puppy?
Yes. If both black parents carry one copy of the recessive brown allele (both are Bb at the B locus), there is a 25% chance each puppy will inherit two copies (bb) and be chocolate. This is why breeders DNA test — you cannot tell by looking at a black dog whether it carries the brown gene.
4Why is breeding merle to merle dangerous?
When two merle dogs (Mm) are bred together, there is a 25% chance each puppy will be double merle (MM). Double merle puppies frequently have severe eye defects (microphthalmia, missing eyes) and deafness. Many are born completely blind and deaf. This is a well-documented welfare concern and is prohibited by many breed clubs and kennel clubs worldwide.
5What is a cryptic merle?
A cryptic merle is a dog that carries the merle gene but shows little or no visible merle patterning. This happens when the SINE insertion in the PMEL17 gene is shorter than typical. Cryptic merles can still produce visibly merle offspring and, if bred to another merle, can produce double merle puppies. DNA testing is the only reliable way to identify cryptic merles.
6Can DNA testing predict exact coat color?
DNA testing can identify the alleles present at each locus and predict the possible colors with high accuracy. However, some modifiers and interactions are not yet fully characterized. Testing gives you probabilities, not guarantees — but for the major loci (E, B, D, K, A, M, S), predictions are very reliable.
7Why are some colors associated with health problems?
The dilute gene (dd) has been associated with Color Dilution Alopecia (CDA) in some breeds — a condition causing hair loss and skin issues in blue and isabella dogs. The merle gene (M) causes eye and ear defects in double merle dogs. White spotting genes in the extreme white pattern (sw/sw) can be associated with deafness, particularly in breeds like Dalmatians and Bull Terriers.
8What makes a Labrador yellow vs black vs chocolate?
Labrador color is controlled primarily by two loci: E (Extension) and B (Brown). Dogs with at least one E allele and at least one B allele are black (E/- B/-). Dogs with at least one E allele but two b alleles are chocolate (E/- bb). Dogs with two e alleles are yellow (ee) regardless of their B locus genotype — the ee genotype blocks all dark pigment from the coat.
9Should I breed for rare colors?
Breeding primarily for color — especially so-called 'rare' colors — is generally discouraged by breed clubs and responsible breeders. Health testing, temperament, and structural soundness should always be the primary selection criteria. Some 'rare' colors in certain breeds (like blue French Bulldogs) are associated with health issues, and prioritizing color over health leads to poorer outcomes for the dogs.
10Where can I get my dog's coat color DNA tested?
Three major providers offer comprehensive coat color panels: Embark Veterinary (tests all major color loci plus 200+ health conditions), Wisdom Panel (color and health), and UC Davis Veterinary Genetics Laboratory (individual locus tests available). Embark and Wisdom Panel use cheek swabs mailed from home. UC Davis accepts cheek swabs or blood samples submitted through your veterinarian.