Siamese — Color Genetics & EMS Calculator

The Siamese is the archetype of the colourpoint phenotype in feline genetics, defined by obligate homozygosity for the cs allele (cs/cs) at the C locus — a temperature-sensitive allele producing a tyrosinase variant that is inactive at core body temperature but active at peripheral extremities. Under FIFe standard, valid SIA EMS codes are restricted to the four traditional point colors: seal, blue, chocolate, and lilac, each arising from the interaction of the B locus (B/b) and D locus (D/d) alleles on the cs/cs colourpoint background. An EMS color calculator for Siamese breeding programs must strictly enforce these four permissible locus combinations and flag non-traditional colors (red, tortie, tabby-point) which belong to the Oriental Shorthair/Colourpoint category rather than the FIFe Siamese standard.

Siamese colour genetics: frequently asked questions

Which recessive colours do Siamese cats commonly carry?
All Siamese are cs/cs. Chocolate (b) is a well-established recessive; heterozygous Bb cats appear seal-pointed. Dilution (d) carriers (Dd) appear non-dilute (seal or chocolate). Lilac-point SIA require b/b + d/d. Some Siamese lines may carry a hidden O allele (red factor) from historic outcrossing, but red-series points are not accepted in FIFe SIA.
What colour restrictions apply to the Siamese breed standard?
Under FIFe, only four colors are recognized: seal (n 33), blue (a 33), chocolate (b 33), and lilac (c 33). Red, cream, tortie, and tabby-point variants are excluded from the SIA register and belong to OSH (Colourpoint). Cinnamon (bl), fawn, and all non-traditional point colors are not accepted. White (W locus) and bicolor are categorically excluded. Solid, tipped, and shaded patterns are genetically impossible in cs/cs animals.
Which coat patterns are typical for the Siamese?
No tabby or bicolor pattern variants are accepted in FIFe SIA. The colourpoint pattern (33) is the sole recognized phenotype. Faint ghost-striping visible on the points of some Siamese does not indicate agouti genotype; it is a developmental artifact. Under TICA and CFA, 'Applehead/Traditional Siamese' may have slightly different color registers, but EMS is a FIFe standard tool.

Popular EMS Colors

SIA n 33Seal Colourpoint (Seal-Point Siamese)
SIA a 33Blue Colourpoint (Blue-Point Siamese)
SIA b 33Chocolate Colourpoint (Chocolate-Point Siamese)
SIA c 33Lilac Colourpoint (Lilac/Frost-Point Siamese)

Calculate Colors for Siamese

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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Enter the appearance of both parents to calculate color predictions.

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