odd eyed , blue eyed & orange eyed
Odd eyed Recessive (dominant on the bottom of the page)
I have tried as good as possible to translate everything into English, I would like to apologize in advance when it is not all correctly translated.
I also want to mention that I am not a geneticist. I wrote this article after research and from personal experience.
A cat with odd-eyed eyes is an animal with one orange, yellow or green and one blue eye. Most common are the fully white cats with this special eye color, but it is also seen in cats that are predominantly white in color with only a few colored coat parts; by (photo 1), harlequin/van and, to a lesser extent the normal bi colors (photo2), in very extreme cases we can find odd eyed in cats without white. In the case of cats without white in odd eyed, the cats I've seen where always black cats, in my opinion this has to do with the silvergene, this is just my opinion that i cannot explain. Because we assume that a cat has to have at least once the white-gen (S) to be odd eyed, it still gives plenty of room or thought when we see that there are also cats without white odd eyed, this indicates how little we know so far about the genetica of odd eyed.
Odd eyed at bi color cats is an autosomal defect, in my opinion a defect is not necessarily negative. In the case of the odd eyed cats it is where we select on the defect of the lack of melanocytes.(Melanocytes are pigment cells that make pigment granules, the pigment of those grains is called melanin)Blue eyes are caused by the lack of the melanocytes in the eyes.
A side-effect is that cats with decreased melanin production coul have a coat that is not always correctly colored like the breed standard desires. Nevertheless it is not a big issue to go to shows with. It is common for odd eyed cats , or cats why carry odd eyed to have a white tail tip. The white tail tip is not considered a big issue also for show inside these bloodlines and most judges do not mind. See the above picture of Rivium's Kissable, a cinnamon white girl with a clear white tip on the tail. (picture 3)
At fully white cats (photo 4) is linked to the genetic factor W (dominant white) This gene can turn of color in the fur and eyes. White cats have a big risk of deafness or hearing impairment. Researchers found that only 17 to 22 percent of white cats with non-blue eyes are born deaf. The percentage rises to 40 percent if the cat has one blue eye, while upwards of 65 to 85 percent of all-white cats with both eyes blue are deaf or have a lower quality of hearing. Some of these cats are deaf in only one ear. Colored cats with white in the coat (bi color,harlequin, van) there are no cases or risks for deafness. In colored cats the pigment is associated with the dominant gene S (piebald white spotting). Recessive odd eyed can be bred without problems.
Kittens are born with a baby-blue eye color, newly born kittens did not created the color for the eyes yet. All kitten are born with blue eyes. At the age of two to four weeks kittens start to create melanine, this melanine is slowly given the eye his color. In odd-eyed cats the pigment production is slowed down in one eye.(Melanocytes are pigment cells that make pigment granules, the pigment of those grains is called melanin). Blue eyes are caused by the lack of the melanocytes. The eye color is determined by the genetic material into the body cells. This material is on the DNA that determines which substances are activated to form an eye color. A substance that is created is among other melanin. In cats with dark colored eyes is much melanin created, in cats with light eyes is very little melanin. Melanin is also find in the hair. Darker colored cats seem to have the eyes change faster as lighter colors. Red and creme cats seem to have sometimes a slower change of eye color. The eyes remain a longer time blue as other kittens with other colors of the litter.
Odd eyed in white cats inherits dominant , it means that only one parent need to pass it on to her/his offspring. Only the white borns can be odd eyed, unless the white cats has also other odd eyed bloodlines in the genes.
Odd eyed at bi-color cats is an autosomal inheritance defect, the "odd eyed gene" must come from both parents, cats can carry this gene (or defect) for generations, I would like to say that there is no such thing as one odd eyed gene, the eye color is an inherited trait that is determined by multiple genes. In autosomal recessive inheritance, both parents has a gene-defect (the gene for odd eyed) and is given on to there offspring , the kitten has inherited from both parents the odd eyed gene.
When the goal is to breed bi color odd eyed cats it makes little sense to breed a white odd eyed (or white odd eye carrier) with a bi color odd eyed (or bi color odd eye carrier), bi color odd eyed kittens will not be born from this combination, these are two different genes. White born kittens can of course be odd eyed because the dominant inheritance rule of white. All kittens out of this combination carry the bi color cat his odd eyed gene, also the white born kittens from this combination will carry the bi color odd eyed gene. Therefor the white kittens can give odd eyed cats with color when mated to another odd carrier later.
Odd eyed or two blue eyes is currently the most rare that you can find at the British shorthair. Bi color odd eyed cats have NO hearing problems, because these odd eyes are bred with bi colors and have nothing to do with the genes of pure white cats.
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Please note that odd eyed cats in Van and harlequin's are recognised by all cat associations, bi color odd eyed is much rarer than the van or harlequin odd eyed, normal bi color is only since 2019 register by FIFE. It's also recognized in LOOF and WCF. Solid odd eyed is not yet registered and will get RIEX (experimental) pedigree. These cats have also a different kind of genes (dominant). More info below on this page.
It also seems that cats with much silver in lines , give more odd eyed (some breeder believe the same about point cats in the bloodline). Also cats with the coat itself in silver or smoke , more often seem to have a much more darkblue eye color. I saw this multiple time in smoke cats, but it is not always the case. The pictures below are examples.
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black smoke blue eyed born with yvie die Hillya de candybelle choc smoke bicolor odd eyed
Another possibility in the eye colors are split , or cracked eyes. These eyes have both orange as blue in them. On show they are not appreciated as much as odd eyed (in theory the eye should completely be blue or orange, but not both.) Personally I find it beautifull. Look at pictures below.
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British gems Sophie : split odd eyed at both sides.
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British shorthair with both eyes cracked , the blue and orange flow into each other
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Blue eye cracked with a part of orange​
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A cat has 48 chromosomes (19 pairs), each chromosome is formed from a strip of DNA, which consists of thousands of pieces, called genes. Chromosomes contain all genetic properties. DNA is located in the nucleus of each cell, actually in the chromosomes in the cell nucleus. A cat has more than 80,000 genes.
The first cells in an embryonic kitten grow into many different cell types. During this development, the cells get their specific function. They develop into brain cells, skin cells or muscle cells. Each cell contains a complete copy of the genetic material of the parents, in the form of chromosomes. With each cell division, a copy is made of all the genetic material. Chromosomes are the carriers of the genes. The chromosomes contain all the genetic information that is necessary to develop, maintain and reproduce an individual.
You can see chromosomes as long strands. These consist of a substance that we call DNA (deoxyribonucleic acid). The DNA contains the code where all our inherited characteristics are recorded.
A gene is a piece of defined DNA that contains the information for the formation of a particular protein. Proteins go to compounds with other proteins and therefore have multiple functions in the body. Genes determine the genetic characteristics, such as the color of the hair and the eyes.
Until now, geneticists have found at least 15 different genes which play a important role in the transmission of the eye color.
DNA studies examines differences or similarities between sick and healthy genes. For defects caused by just one gene mutation can be developed a DNA test, when multiple genes play a role, as in odd eyed, the possibility of a DNA test does not yet exist.
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Dominant odd eyed (some small but important information):
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What is the difference between dominant and recessive? With recessive both parents should be from odd eyed bloodline to be able to produce odd eyed kittens. With dominant only one parent should be odd eyed and can produce kittens with odd eyed with any partner. This resulted into many cattery wanting to buy dominant gened cats. Dominant cats are in a higher priceclass. The problem is that dominant genes should not be bred to another cat who has dominant genes to prevent serious health issues and many cattery do not care about the risks , they will sell anything into breeding for profits. Many cattery do not inform the buyers (enough) about how to breed with these cats or do not even tell the buyers that the cats are from dominant odd eyed lines. Since there is no EMS code for these cats , it is not visible in pedigree and mistakes can easily happen. Therefor it would have been good that dominant cats would have become a whole new breed , but the damage is already done and at this moment a lot of british have dominant lines in the pedigree. There are some breeder who did produce a new breed with dominant because of these reasons.
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At this moment there are some studies going on (Marie abitol for example) to locate the genes of dominant cats and about the health.
What is this gene: a cat that has a minimal white variegation (small white spot of a size of a hazelnut to a coffee saucer) and two intense blue eyes, odd or polychromic, or latent (non-expression of blue eyes, but still carrier-dominant!). Lately dominant are getting less and less white (sometimes no white is visible anymore). To obtain these genes and eye color it is necessary that the pedigree cat is crossed with an Altai, Ojos Azules or Topaz cat (these are the lines that exist in dominant). The cats with these genes have been found in the wild as a spontanious mutation and mated into different breeds worldwide. The first blue-eyed cats were discovered among stray cats in Kazakhstan's Altay region in the 1990's. Only much later, when the Altai gene became more and more famous and popular in breeding, blue-eyed beauties in nearby and other regions of Kazakhstan where passed on to breeders of various breeds in Russia, Ukraine and other regions and spread from there to the rest of the world.
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What is the danger? Deafness (Altai, Topaz) cranial malformations (Ojos Azules, a breed abandoned by the LOOF and the Tica in 2004 because of issues). Other things commonly seen in dominant odd eyed is a kincked tail or nose shapes that are strange (of form and small or not equal nostrils). Also because dominant comes from wild cats and is only bred very recently, the type still has a lot of work to do to improve to a true british look. Dominant to dominant also seems to produce kittens with a large amount of white even if the parents are solid.
Special feature of this gene: DBE kittens (intense blue and odd eyes) in solid colors with possibility of a locket (white spot that is a traitmark of the genes) often located in the neck , on the toes or face. Kittens with this dominant gene can be "latents" with orange eye colour but they will also be able to produce odd eyed kittens!
To reduce the danger that this gene represents, here are the STRICT recommendations of PROFESSOR MARIE ABITBOL working with Vetagro research laboratorium.
DO NOT BREED DBE BLOODLINES WITH :
- Colourpoint", or colourpoint carrier
- Cats who have white" (bicolour, harlequin, van ) if you want to breed odd eyed with white, just work with recessives. It already exists!
- Pure White cats
- Cats born from DBE marriages and others who are born "LATENT" with orange eyes.
- Recessive odd eyed (since these cats often have white and breeder often sell kittens with white in dominant into breeding, people could mistake the bloodline as a recessive since there are recessive bloodlines in the pedigree and by accident later make a wrong combination that influences the health. Again only solid cats with odd eyed should be allowed to go into breeding.
Mixing (accidentally or not) a dominant cat to another dominant cat even if latent , can cause severe health issues in the first or future generations and should never be done. This is the reason cats who are latent (orange eyed born from dominant cats, should be sterilised and removed from breeding! Also wrongly bred cats who are dominant and are bicolor van or harlekin , should be sterilised and not be used for breeding. This is to prevent mistakes happening and accidentally breeding dominant to dominant since there is no ems code to say the cats are dominant. People could mistake the dominant cats who are latens as normal orange eyed bloodlines or the odd eyed for recessive. By breeding the bloodlines correctly only solid odd eyed dominant would exist and no mistakes would happen!
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Some breeder have been able to write on the pedigree that their cats are dominant genes , this is also a possibility to breed safely and prevent mistakes and is also a good solution!
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Please share this information widely as many breeders are are not aware of it. We are thinking especially of the starting breeders or breeders who never worked with odd eyed cats who could read DIRECTED AND INCOMPLETE information or do not receive this info from the breeders they buy from.
These are the guidelines to breed responsible with DBE until enough is known about the genes and to prevent accidental wrong matings that cause severe health issues. They do have higher risks as other cats or recessive genes so they should be bred responsible. Keep dominant cats in solid color only , this is what makes them unique ! And all the risks of ''mistakes'' would be reduced dramatically if everyone would do this.
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I do not want to discourage people to breed with dominant. Buy your cats from the right breeders , breeders who help you understand how to breed with the genes and support you in your breeding when you are learning. They are beautiful cats. Just do it in a responsible way so that in the many years that are still to come , the british breed stays healthy. More and more dominant will pop up in bloodlines and more and more issues could arise. Inform yourself, think very well about it and if you want to follow the guidelines and if you want to breed it for the right reasons and not because of the higher price class (if not , DO NOT DO IT).
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Other eye possibilities:
Why there is no dna test:
