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Siamese Genetics

Discussion in 'Cat Breeding' started by Leslie49, Feb 24, 2020.


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Am I correct..?

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  1. Leslie49

    Leslie49 PetForums Newbie

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    Hi me again. Still trying to get things clear in my mind.... !!! I’m posting because I don’t know the answer. So, its not helpful if you tell me I should know the answer....! ☺️
    So, here goes. I was approached at a show to join a certain Siamese cat club. We got chatting and somehow got around to talking about colours etc. My understanding was... and yes you already know that I know very little... however I was sure I was right on this particular point. Genetically a Seal Point Siamese is the same as if it was black. Before you all start rushing to tell me.... I know Black doesn’t exist in Siamese as the Siamese gene lightens black to seal. Am I correct so far before I continue?
     
  2. OrientalSlave

    OrientalSlave Shunra Oriental Cats

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    To quote Langford:

    "The Colour gene (Tyrosinase, TYR) has four alleles (C, cs, cb and c). The wild-type allele (C) is dominant and produces full colouration. The cs and cb mutations cause temperature sensitive pigment production that is characteristic of Siamese colourpoint and Burmese colouration, respectively. The c allele is rare and causes full albino colour.

    Two copies of the Siamese allele (cs) are required for Siamese colouration. The Siamese mutation restricts the pigmentation to the points."

    Colour is restricted to the points because they are cooler.
     
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  3. Tigermoon

    Tigermoon PetForums VIP

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    Seal is black. The hair can look a paler brown because there is usually a lighter base due to the way the colourpoint gene works, but the hair is definitely black.
     
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  4. Leslie49

    Leslie49 PetForums Newbie

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    Absolutely what I thought. This person said chocolate was the dilute of seal. However I think blue is the dilute of seal? And chocolate carries a different gene altogether.
     
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  5. Tigermoon

    Tigermoon PetForums VIP

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    I seem to recall someone on the forum once explaining that there was only Black and Red and the rest were all dilutions or modifiers of those two colours. It was a long time ago and I can't remember who said it now.
     
  6. Tigermoon

    Tigermoon PetForums VIP

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    So one of the genetic test labs says this:

    Brown
    The Brown (tyrosinase-related protein-1, TYRP1) gene affects the amount of black (eumelanin) pigment produced. Mutations responsible for brown and cinnamon colors in the cat have been identified in this gene. The wild-type B allele produces normal, black coloration. The b allele produces the brown (chocolate) phenotype and the bl allele produces a light brown or cinnamon phenotype.

    Dilute
    The dilute gene (Melanophilin or MLPH) causes clumping and uneven distribution of pigment granules in the hair shaft, producing dilution of all coat colors. Dilute is an autosomal recessive trait which means that two copies of the dilute allele are needed to produce the phenotype. Black pigment is diluted to gray (blue is the term used by cat breeders), and red is diluted to cream.
     
  7. Rufus15

    Rufus15 PetForums VIP

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    Chocolate is a recessive to black, blue is a dilution to black :)
     
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  8. gskinner123

    gskinner123 PetForums VIP

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    Chocolate and lilac can be very confusing to anyone new to colour genetics. We refer to chocolate as being 'carried' and to some this translates into being a recessive colour and therefore the dilute of black.

    Then you try explaining that your, for example, Blue BSH carries chocolate which further reinforces the belief that chocolate is dilute!
     
  9. QOTN

    QOTN PetForums VIP

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    I would love to know which breed club it was and what exactly was the objection to the idea of seal being the Siamese expression of the black gene.

    I think there is great confusion generally between colours and patterns. A sealpoint Siamese is a black colour but with the restriction of colour to the points which is a pattern.

    Dominance is such an important factor and is often misunderstood. There are three cat colours all at the same locus. Black is the wild type as mentioned before and is dominant to both chocolate and cinnamon which are the mutations. Chocolate is dominant to cinnamon. All cats have two colour genes, one inherited from each parent.

    Dilution has already been mentioned as changing the appearance of the basic colour genes not replacing them.

    Similarly the red gene and the white gene mask the basic colour genes but they are still present
     
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  10. lillytheunicorn

    lillytheunicorn PetForums Senior

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    @Tigermoon you are correct, all cats are either red or black as there are only two different types of pigmentation eumelanin (black) and phoeamelanin (red). The other colour genes modify the expression of these colours. https://pawpeds.com/pawacademy/genetics/genetics/redorblack.html

    The modifications at the B-locus Black, Chocolate and Cinnamon only affect the eumelanin pigment. So you can have a cat who has two chocolate genes who is red as that modification does not affect the phoemelanin pigment.
     
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  11. Leslie49

    Leslie49 PetForums Newbie

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    Thank you so much for this... you have made my day!! I’m just returning to breeding after a gap of many years. I’ve forgotten a lot of what I knew but was sure I was right on this point. The person who challenged me has been breeding for 30 years. So turns out I’m not as green as I thought.
     
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  12. Maurey

    Maurey butler to a spoiled kitty

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    Something to keep in mind, as well, is that red is epistatic (dependant on) to non-agouti, meaning that for a cat to be red, it also has to be a tabby.
     
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  13. Leslie49

    Leslie49 PetForums Newbie

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    I will not mention who this was but the conversation was about seal points vs chocolate points and who carried what etc. I said there’s a chance she carries dilute as her father was blue. He then went on to say that chocolate was the dilute form of seal. To which I was stunned but wasn’t confident enough to disagree.
     
  14. Maurey

    Maurey butler to a spoiled kitty

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    Oh dear >>;; And this person say they're an experienced breeder of 30 years? Even as a hobbyist interested in cat genetics (and admittedly a bit of a human geneticist by profession, and, as a consequence, a bit of a genetics nerd), I know better >>;; Where does this person think Lilac and Blue come from???
     
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  15. Leslie49

    Leslie49 PetForums Newbie

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    My understanding of this is that although all red cats will “appear” tabby. Genetically they can be either.
     
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  16. Leslie49

    Leslie49 PetForums Newbie

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    Well it was kind of the end of the conversation as I was dumb struck!!
     
  17. Maurey

    Maurey butler to a spoiled kitty

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    This is true, yes! This is generally known as 'ghosting', and is also commonly seen in black cats who seem to have barring on the tail, or on the legs, though black cats often grow out of it, afaik c: All cats who are shown as 'red solid' (which, yes, is a classification, for some reason), are really minimally-expressed ticked cats, typically, at least based on some of the standards I've been reading. I don't really understand why they need a category of their own, but I suppose the red tickies that pass for solids would have faults for markings as ticked cats lmao
     
  18. Rufus15

    Rufus15 PetForums VIP

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    Not at all. I have two red solids (well a solid and a smoke) here, tabby is genetically impossible for them. I think what you mean is that one can see the tabby pattern more obviously in a red solid
     
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  19. Maurey

    Maurey butler to a spoiled kitty

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    It is, yes! I meant that they will typically have a lot of tabby ghosting, and that generally the cats that look solid will be minimally-expressed ticked cats.
     
  20. Rufus15

    Rufus15 PetForums VIP

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    No. Ticked is a tabby pattern and tabby is genetically impossible, neither parent is tabby. Neither of my kittens have a lot of tabby ghosting either, they're quite minimal as they should be.
     
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