'Fawn' (the "b" & "d" influences combined)

 This post looks at the previous series of influences in their dilute forms ("b" and "d"). What we will look at now is the interesting colour that is expressed when these two dilutes are combined (or both recessives are present) on a dog. The only phenotype where this happens is "bb" "dd".

First, we'll revise these colours quickly. Using the Australian Kelpie as an example, we can first see the dilute brown series "bb" and its effect on the colouration of the dog. As previously discussed, we note that all black pigment is diluted to brown.
Here we have a diluite 'brown' dog, also called Red and Tan in Kelpie language. All black pigment is diluted to brown, and we now know this dog's phenotype to be"bb". The dog may also be carrying "d" - in which case, this dog could produce a combined dilute.

The next Kelpie here [pup] as we see, is a dilute black of the next series. He is diluted in a different way - the black is turned to a grey/blue colour. This dog, as we discovered previously, is "dd". It may also be a cariier of the above series, and its phenotype may be "Bb". Now is when our genetics get interesting. We now come across the unusual and hard to come by colour, 'fawn' (or blue fawn). This colour is actually falsely labelled and is not, in any way, a fawn colouration, nor is it affected by the same alleles that produces red Dachschunds or cream Golden Retrievers.

Here we see two examples of these 'fawn' coloured dogs. Both mother and pup here are the same colour. Put simply, this version of 'fawn' or 'blue fawn' is the result of blue and brown dilution genes working together. (It might be easy to imagine the two above dogs, red and blue, bred together. They would produce the dilute fawn colouration.) This colour could be called a double dilute, which it is in various terms, but it is actually a combinational dilute where two recessives work to combine and produce a different product. The phenotype of a dilute 'fawn' is always "bb" dd".

As with the other two dilute black series, this multiple dilution also causes the lack of melanin to be created in the coat. We can see here the eyes and nose of a Doberman of this 'fawn' colouration, and, looking closely, can notice that this dog's skin and colour is particularly lighter than even the light brown dilutes. This is apparently because there are two genes in dilution here, not just the one. This dog also posseses very lightly coloured eyes, and as with blues, these may come in amber, green or even blue. The eyerims are also quite light - a common health problem with this colour is that these animals are affected by bright sunlight - due to the lack of protective pigment around the eye. We make note, again, that despite this dilutedness, the tan points still have not changed! Again, this is the result of a different influence and it is not uncommon to have some fawns a similar colour or even lighter than their points!
In some breeds, this colouration is referred to as 'Blue Fawn', 'Fawn', 'Isabella'; and, in the Border Collie it is known as 'Lilac'.

Here we have an example of a 'Lilac' Border Collie. It is not quite chocolate, not quite fawn either, yet is a beautiful colour. The reason this colour is often referred to as Lilac is because these dogs often appear to have a 'purple' sheen. There are various theories on why this is so, but a common thought is that while the genes combine, they can have a tendency either way, and it appears to be chocolate with a little blue coming through - hence the purple term. 

Here is another Border Collie, only this puppy displays tan points. These points are quite light, making them almost invisible when compared to the coat colour. Note the almost pink nose and blue eyes as can be seen on this dog, typical of the dilutedness. We can establish that because this dog has tan points, it must be "kk" - it is also a dilute of brown and blue, so it is "bb" "dd".

Now, let's look at genetics.

Here I have included a simple example, which is not always the cause of this colour pupping up. Still, here we have a punnet square using a blue dog bred to a chocolate dog. (This is merely an example, obviously there are many more combinations possible.)This type of breeding is often deliberate and with the intention of breeding this colouration.

Here is also an example of one way this colouration is produced. (Note - this punnet square is not nearly big enough to show all possible offspring, but one gets the general idea as to how these offspring do come about.) It is often rarer to have a 'fawn' or 'lilac' dog produced from obviously black parents. The reason this happens is because both parents carry a set of the dilution gene which is only expressed when both sets match up. Apart from these expressions, it is also common for parents carrying these dilute genes to throw blue and chocolate pups. So, just quickly: dogs with genotype "Dd" Bb", "dd" Bb", "Dd" bb" bred to another carrying this dilution will produce isabella puppies.