"COPPER" PHENOTYPE IN BRITISH TIPPED SHORTHAIRS (ULTRA-WIDE-BAND)
This article looks at the appearance of "ultra wide-band" in Tipped and Shaded Golden British Shorthairs. These are also known as Golden Chinchilla and Golden Shell. The term "copper" was adopted by Linda Petersson Wahlqvist to describe Golden Shell cats with white toes, white undersides, golden colour with the dark tips (e.g. black or blue) restricted to the tail tip and an absence of dark nose-liner. These phenotype deviates from the standard for tipped cats, but is becoming prevalent in Russia and in some German lines of British Golden Shorthairs. "Copper" is not an official term, but it allows breeders to describe the phenotype in a single word.
Shaded and tipped (shell/chinchilla) are due to the dominant Inhibitor gene (silver) + presence of Wide Band + the Ticked Tabby pattern. Insilver cats the dominant Inhibitor is present. In golden cats, the dominant Inhibitor is absent. Wide Band is independent from the Inhibitor gene and though "Wb" is treated as a single dominant gene for simplicity, it appears to act as polygenes with an additive effect. In ticked tabby cats without silver, Wide Band restricts the pigment to the end of the hair leaving a pale golden band between the skin and the pigment. Through selective breeding, this effect has been maximised. The variability of the wide band suggests we should talk about Wb, Wb+ and Wb++ to describe cats with normal, intermediate and greater degrees of Wide Banding.
The appearance of this phenotype was investigated by tracing the family trees of cats that displayed it. This showed that there was no single mutation or common ancestor, but rather it was the interaction of mackerel tabby (ny25) with chinchilla (ny11) and most likely an accumulation of Wide band polygenes. Alongside the "copper" phenotype were some chinchillas where the black pigment at the hair tips was reduced to almost nothing. Only the eye colour and paw-pad colour showed that these were truly Chinchilla cats and not solid white cats. This shows that the Ultra Wide Band effect operates on cats with silver as well as without silver. Cats without silver and without Wide Band are cool-toned ticked tabbies. Because ticked tabby is on a different locus from classic/mackerel/spotted tabby, these markings can sometimes breakthrough the ticked pattern to some degree.
Another possibility is a recessive allele (gene variant) at the E (extension) locus, such as "amber" (seen in Norwegian Forest Cats). These usually reduce the amount of black and the effect can range from no black whatsoever (seen in chestnut horses) or still allow some black (as in amber cats) while not affecting the skin pigment. Amber cats are basically black cats with a colour modifier that affects the deposition of pigment on the hair shaft; in non-agouti ambers the nose remains black and in agouti cats it remains pink. The "copper" cats with black pawpads and tail-tips, but without black on the body are suggestive of a recessive E allele.
A further possibility would be a new dominant mutation at the A (agouti) locus. In dogs, this creates the fawn/sable colour, often with black shading or tipping long the spine. Similar dominant A alleles occur in several other mammal species. In domestic cats agouti (ticked hairs) and non-agouti (self/solid colour) are well known. It is possible that unidentified mutations of the A gene have occurred in the domestic cat and are showing up through selective breeding for colour. At least two other variations at the A locus occur in wild cat species.
A mutation at the E locus or A locus would still interact with any Wide Band polygenes to further restrict the colour on the hair shaft.
The following colour-coded family trees should be opened in new windows so they can be read at full size! They show the relationship between ny11 and ny25. They don't answer the question of what gene(s) cause the copper phenotype. They are aimed at showing common ancestors of copper cats and different combinations that have led to the copper phenotype.
Then came the question of how many lines traced to a Persian Shaded Golden called Esteban von Aemstelhove (or van Aemstelhove). Mated to Marvellous Golden Desiree, he produced Goldstern de Broekloni who was a prolific stud used in Silver and Golden British Shorthairs. Esteban von Aemstelhove was noted for his very warm golden coat and it seems likely he had a very good Wide Band trait that was passed down in his descendants. His great-great grandson was Marvellous Gold Radetzky, another prolific stud who appears behind several "copper" British Shorthairs. According to the databases, Esteban von Aemstelhove's other offspring remained in the Persian/Exotic gene pool.
This can be traced even further bck to another common ancestor called Polar Jenko.
So now to trace Marvellous Golden Desiree and Marvellous Golden Radetzky (highlighted in previous trees) back to Persians, American Shorthairs and Scottish Fold Shorthairs. Rather naughtily, the American Shorthairs are shown on some databases as BRI (British) which hides the ancestry of some of the cats. I've highlighted the outcrosses and noted the breeds, and also highlighted a couple of influential cats. Behind some of the "copper" lines are ny12 Persians (I haven't traced further back). It's obvious that these outcrosses will result in British Longhairs further down the line.
Below shows Persian and Exotic Shorthair influences. This moves the British Shorthair even further away from its original type and closer to the Persian/Exotic type as well as affecting the silver and gold colours.
Now to look at some of the other cats that have sneaked into the British Shorthair gene pool (as a request from breeders wanting to avoid those influences). Nirvani Du Mouli D'Amelghem is descended from Scottish Fold straight-eared variants. Sunnyland lines and Goldenen Winkel lines trace back to Selkirk Rex variants. British Shorthair is an allowable outcross for Selkirk Rex, but the straight-haired variants don't usually go into British Shorthair lines. You can also see that Andy vom Wahrberg was a prolific stud who has also contributed to Selkirk Rex lines.
THE CHOCOLATE CONNECTION
Johanna Nordin (Sweden) has also been investigating the copper phenotype from another direction. Her first thought when she saw the red-white golden cats was the Abyssinian sorrel colour, which is cinnamon + ticked, and she started thinking that the cinnamon allele of the bl gene might have a role in the copper cats. She discussed this with an experienced breeder of golden and silver British Shorthairs who has been breeding them for some decades. The breeder told her that the "coppers" are carriers of chocolate and that there might be some crossbreeding with Abyssinians in the copper-lines but that was not the official standpoint.
Johanna then went on to check out the expression of the chocolate colour in Abyssinians (23b). Chocolate ticked Abyssinians resemble the red-white golden coats of the "copper" British (such as Sundust Macavity), but with the addition of having more white on the chin and toes. They also had the same black at the end of the tail tip. In Abyssinians the colour is described as “rich copper brown ticked with dark chocolate; Base Hair - Rich Apricot.” So perhaps the copper cats are ticked chocolates with Wide band (and maybe other polygenes) and without inhibitor (golden ii = non silver). This could explain why the coppers have more white on the chins, toes and undersides than the Abyssinians (which don’t have the wide band and other polygenes) and a lighter base colour. Side by side, there is a similarity, allowing for the brighter and more whited appearance of the copper shorthairs.
If the coppers were tested and found to be chocolate and cinnamon, that would make them (in EMS terms) "chocolate golden tipped/ticked = by 11 (25)" or "cinnamon golden tipped/ticked = oy 11 (25)."