Chartreux — Color Genetics & EMS Calculator

The Chartreux is one of only two pedigree breeds (alongside the Russian Blue) genetically fixed for a single EMS color code: blue solid (a), arising from obligate homozygosity at both the Agouti locus (a/a, non-agouti/solid) and the Dilution locus (d/d, dilute), with no exceptions recognized under FIFe or any major international registry. The breed's identity is inseparable from this dual homozygous genotype, producing the characteristic blue-gray coat with the distinctive 'breakable' woolly texture; any other color phenotype arising from Chartreux breeding indicates undisclosed outcrossing or incorrect registration and is a disqualifying fault. Feline genetics programs for Chartreux are the simplest in terms of EMS color calculator scope, but breeders must remain vigilant against the introduction of non-blue alleles from any outcross or registration error.

Chartreux colour genetics: frequently asked questions

Which recessive colours do Chartreux cats commonly carry?
All Chartreux are fixed homozygous a/a (non-agouti/solid) and d/d (dilute). Unlike the Russian Blue, the Chartreux standard and historic gene pool is considered closed to outcrossing; no hidden chocolate (b) or cinnamon (bl) alleles should be present in a pure Chartreux line. The B locus should be fixed at B/B (black series) in all Chartreux, producing blue only in combination with d/d.
What colour restrictions apply to the Chartreux breed standard?
Only blue solid (EMS: CHA a) is recognized under FIFe standard. All other colors, tabby patterns, bicolors, silver/smoke, and colourpoint variants are categorically excluded. Dominant White (W) is not permissible. Non-blue Chartreux offspring from registered Chartreux parents must trigger investigation into pedigree integrity. The breed is fully restricted to a/a + d/d + B/B genotype.
Which coat patterns are typical for the Chartreux?
No pattern variants are accepted. Ghost tabby barring may be visible in kittens (a developmental artifact) but clears in adults. Any persistent tabby pattern in an adult Chartreux is a disqualifying fault indicating hidden agouti (A/-) allele. Smoke and silver phenotypes are not recognized and would indicate a non-Inhibitor-fixed population issue.

Popular EMS Colors

CHA aBlue (solid) — the only recognized color for the Chartreux

Calculate Colors for Chartreux

Free online cat color genetics calculator. Select the breed and appearance of the sire and dam to predict kitten coat colors, patterns and probabilities based on feline color genetics.

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