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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:
| 24 | Seal Point |
| 24a | Blue Point |
| 24b | Chocolate Point |
| 24c | Lilac Point |
| 24k | Cinnamon Point |
| 24n | Caramel Point |
| 24r | Fawn Point |
Siamese cats with one or two dominant agouti genes are classified under breed 32 as Tabby Points:
| 32 1 | Seal Tabby Point | 32t1 | Seal Tortie Tabby Point |
| 32 2 | Blue Tabby Point | 32t2 | Blue Tortie Tabby Point |
| 32 3 | Chocolate Tabby Point | 32t3 | Chocolate Tortie Tabby Point |
| 32 4 | Lilac Tabby Point | 32t4 | Lilac Tortie Tabby Point |
| 32 5 | Red Tabby Point | ||
| 32 6 | Cream Tabby Point | ||
| 32 7 | Cinnamon Tabby Point | 32t7 | Cinnamon Tortie Tabby Point |
| 32 8 | Caramel Tabby Point | 32t8 | Caramel Tortie Tabby Point |
| 32 9 | Fawn Tabby Point | 32t9 | Fawn 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:
| 32a | Red Point |
| 32b1 | Seal Tortie Point |
| 32b2 | Blue Tortie Point |
| 32b3 | Chocolate Tortie Point |
| 32b4 | Lilac Tortie Point |
| 32b7 | Cinnamon Tortie Point |
| 32b8 | Caramel Tortie Point |
| 32b9 | Fawn Tortie Point |
| 32c | Cream 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 gene | Female: two O genes | Male: one O gene | ||||
|---|---|---|---|---|---|---|---|
| 24 | seal | 32b1 | seal + red | 32a | red | 32a | red |
| 24a | blue | 32b2 | blue + cream | 32c | cream | 32c | cream |
| 24b | chocolate | 32b3 | chocolate + red | 32a | red | 32a | red |
| 24c | lilac | 32b4 | lilac + cream | 32c | cream | 32c | cream |
| 24k | cinnamon | 32b7 | cinnamon + red | 32a | 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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