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  A Brief Introduction to the
  Genetics of the Red Series
  in Siamese Cats

Siamese cats with no agouti gene and no orange gene constitute the breed 24 series:

24Seal Point
24aBlue Point
24bChocolate Point
24cLilac Point
24kCinnamon Point
24nCaramel Point
24rFawn Point

Siamese cats with one or two dominant agouti genes are classified under breed 32 as Tabby Points:

32 1Seal Tabby Point
32t1Seal Tortie Tabby Point
32 2Blue Tabby Point
32t2Blue Tortie Tabby Point
32 3Chocolate Tabby Point
32t3Chocolate Tortie Tabby Point
32 4Lilac Tabby Point
32t4Lilac Tortie Tabby Point
32 5Red Tabby Point
32 6Cream Tabby Point
32 7Cinnamon Tabby Point
32t7Cinnamon Tortie Tabby Point
32 8Caramel Tabby Point
32t8Caramel Tortie Tabby Point
32 9Fawn Tabby Point
32t9Fawn Tortie Tabby Point
32 10 Apricot Tabby Point

The group of Siamese with which the Red Point & Tortie Point Siamese Cat Club is concerned have no agouti genes, but have one or two genes for orange 'O', and are classified:

32aRed Point
32b1Seal Tortie Point
32b2Blue Tortie Point
32b3Chocolate Tortie Point
32b4Lilac Tortie Point
32b7Cinnamon Tortie Point
32b8Caramel Tortie Point
32b9Fawn Tortie Point
32cCream Point
32fn Apricot Point

The red colour in these cats is sex-linked, the O gene being carried on the X chromosome. There is no O gene on the Y chromosome.

Females have two X chromosomes, so can have two O genes - making a red, cream or apricot, one O gene - making a tortoiseshell, or no O genes - making a seal, blue, chocolate, lilac, cinnamon, caramel or fawn cat.

Males have one X and one Y chromosome, so either have one O gene - making a red, cream or apricot cat, or no O genes - making them seal, blue, chocolate, lilac, cinnamon, caramel or fawn. A tortoiseshell male cat is a genetic abnormality.

The dilution gene is recessive and, when present in a double dose, dilutes seal to blue, chocolate to lilac, cinnamon to fawn and red to cream. The dilute modifier gene (dominant) converts blue, lilac and fawn to caramel and cream to apricot. As Blue, Lilac and Fawn Tortie Points must have a double dose of the dilute gene they must show cream and cannot show red on their points. Similarly, Caramel Tortie Points must show apricot, not red, on their points, although this may appear very "hot" in colour.

The Red series of Siamese is directly related to the 24 series as follows:

Male/Female: no O genes Female: one O geneFemale: two O genes Male: one O gene
24 seal32b1 seal + red 32ared32a red
24a blue 32b2blue + cream32c cream32c cream
24b chocolate 32b3chocolate + red 32ared32a red
24c lilac 32b4 lilac + cream 32c cream 32ccream
24k cinnamon32b7cinnamon + red32a red 32a red
24n caramel 32b8 caramel + apricot 32fn apricot 32fn apricot
24r fawn 32b9 fawn + cream 32c cream 32c cream

The Club also produces comprehensive breeding charts detailing the kitten colours which may be produced from different Siamese matings.


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