Friday, January 4, 2013

Recessive Red (the "e" influence)

Ah, the beautiful Irish Setter. Also commonly known as the 'Irish Red' breed of dog, this breed is a particularly good example of recessive red the 'e' series. Firstly, I will point out a few things so we can establish what series the colour is produced from. We already can see this dog is not black, nor blue. We may think it is a dark shade of the brown dilution gene, however - if we remember correctly, brown dilutes are dilutes all over. Notice carefully that these dogs have black noses, dark eyes and eyerims. They are still genetically black, and not a dilute. Now we will look at the "e"/"E" series. If this dog was dominant "E" (red seen, black hairs present - i.e. sable) it would be fairly easy to find black tipped hairs on the body. It is well known that Irish setters come in red and red only. If they were indeed sables, chances are a few tanpointed patterns would appear every now and then. We know for a fact this never occurs in the 'red' breed. This rules out any form of agouti expressions. Therefore, these dogs would be "KK" ("BB" & "DD also.) Now we will look at the "E" series. "E" dominant E is the Red/Black expression only when agouti is present. As we know, these dogs are not any form of agouti. Therefore, they are the recessive expression of E. ("ee") This homozygous pair of recessive 'e' means that the body colour is recessively coloured independantly to the black colouration. Therefore, any "ee" in any phenotype means a red dog. Or, in some cases, whichever shade of red is present. This is how we get 'blonde and white' Border Collies or true 'fawn/cream' Kelpies - when the colour is not as strong as dark red, but still expresses on the recessive red series.
Now to explain how the black works here. Because we established that red is only a coat colour (this is the expression of phaomelanin, not eumelanin) the skin, eyes, nose and eyerims are not changed. Thus, if our dog is "KK" "BB" "DD" - he will have black in all of these areas. (Hence our black-nosed Red Setter.) If our dog is genotypically "bb', for instance, he will have a chocolate coloured nose and skin, and red or cream/lighter body.
Example of the nose leather of an Irish Setter dog. Its body is very deep Red, however the nose is stark black. The eyes are also dark. We have established this is due to two colourations being expressed - "KK" for the black, and "ee" for the red.

Another breed well known for its colouration is the Golden Retriever. This breed comes in one colour only; with the exemption of the actual colour coming in a variety of shades. This breed is an excellent example of a breed of dog that expresses this recessive red principle. Golden Retrievers are cream, gold, or sometimes near-white. As no black or forms of black are present, we know this breed is therefore "KK" "ee". We also notice that most Goldens have dark black noses, etc, with the exception of  a few chocolate/brown based dogs.

The same influence at work - this 'blonde' Border Collie is another example of the recessive red influence. Because there are no black hairs at all, this dog is obviously a recessive red. It also expresses "KK" as can be seen by the black nose. This dog is "KK" "ee".

An example of a true fawn, or 'cream' Australian Kelpie. This dog is recessive red and does not express any forms of tan pointing, dilute fawn, or blue. This dog may be similar in colour genetics to the breed's forebearer, the Dingo. Recessive red "ee", which is most likely the majority of Dingo expressions, is easliy dominated by dogs carrying "E" - hence why when bred to black/pointed dogs the cream colour became reduced in the genepool.
This colouration, a light, sandy coloured red is often called 'Fawn' (the true term for this shade of red) and is determined by the same influence which determines the colour of a dog's tanpoints if they express that pattern. Recessive reds do not express any form of agouti. (No sable, no tanpoints may be expressed. If they are, the dog is not recessive red, but rather, dominant red.)

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