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French Bulldog & Exotic Bully “Coat Color” Calculator

Coat Color Genetics Calculator

For French Bulldogs & Exotic Bullies

Determine Parent Genetics

Answer a few questions about the Sire (Dad) and Dam (Mom) to estimate their DNA.

👨 Sire (Father)

👩 Dam (Mother)

Select the exact alleles for each locus.

Locus Sire Alleles Dam Alleles

Deep Dive: The Science of French Bulldog Color Genetics

Genetic coding is the blueprint of life. In French Bulldogs and American Bullies, coat color is determined by the interaction of multiple gene locations (Loci). Understanding these interactions allows breeders to predict offspring traits with mathematical precision using Punnett Squares.

🧬 Loci Glossary: The Genetic Alphabet
  • A-Locus (Agouti): Controls the base pattern. Ay (Fawn) is dominant over at (Tan Points) and a (Solid Black).
  • D-Locus (Dilute): The “Blue” gene. Recessive d/d dilutes black pigment to grey (Blue).
  • B-Locus (Testable Chocolate): Controls liver pigment. Recessive b/b creates Testable Chocolate.
  • Co-Locus (Cocoa): A unique French Bulldog brown gene identified in the HPS3 gene [1]. Creates a darker chocolate than B-locus.
  • E-Locus (Extension): Controls masking. Em gives a black mask. Recessive e/e (Cream) turns the dog off-white and hides all other colors (black, blue, merle, etc.).
  • K-Locus (Dominant Black): Kbr causes Brindle striping, which is dominant over non-brindle.
💎 Rare Colors Explained: Isabella, New Shade, Platinum

When recessive genes combine, they create rare “dilution” stacks:

  • Lilac: Blue (d/d) + Cocoa (co/co). A visible light purple/grey.
  • Isabella: Blue (d/d) + Testable Chocolate (b/b). A champagne-like, dusty rose grey.
  • New Shade Isabella: The “Trifacta”. Blue (d/d) + Testable (b/b) + Cocoa (co/co). The lightest, most premium variation.
  • Platinum: Any of the above combinations masked by Cream (e/e). A Platinum dog looks white/cream but carries the DNA for Lilac, Isabella, or New Shade.
⚠️ Health Warning: The Double Merle Risk

Never breed two Merle dogs together (M/M).

While the Merle pattern (M/m) is striking, inheriting two copies of the gene (M/M) is linked to severe health defects known as “Double Merle” or “Lethal White”.

Scientific studies confirm that Double Merle dogs are at significantly high risk for:

  • Microphthalmia: Abnormally small or malformed eyes [2].
  • Congenital Deafness: Partial or total hearing loss due to lack of pigment in the inner ear.
  • Iris Coloboma: Clefts or holes in the iris structure.

Responsible breeding requires testing parents to ensure one is Non-Merle (m/m).

References:

  1. Mock, L. et al. “Novel Brown Coat Color (Cocoa) in French Bulldogs Results from a Nonsense Variant in HPS3”. Genes, 2020. [Link describes the distinct genetic basis for Cocoa vs Testable Chocolate].
  2. Strain, G.M. “Deafness prevalence and pigmentation and gender associations in dog breeds at risk”. The Veterinary Journal, 2004. [Detailed study on pigmentation-linked deafness in varying breeds including merle carrying breeds].