The inheritance of coat colours in the French Bulldog
By Chris Jefferies(Chrishell French Bulldogs NZ)
The first thing that must be appreciated is that the French Bulldog is a FAWN dog, or at least its base colour is.
I have tried to keep things as simple as possible by not including the gene locus, which tends to confuse the issue. Instead the actual colour word has been identified without the gene code make up, so if you know what is dominant and what is recessive you should be able to work out what the potential outcomes are or determine how a certain feature eventuated.
Brindle is the dominant gene, which is a pattern, not a colour. It consists of black hair overlaying the fawn ground colour and its degree of intensity determines the visual perception, ranging from almost black, through light brindle, to a tiger stripe (sometimes incorrectly referred to as reverse brindle)
Reverse brindle terminology used correctly identifies an almost Black looking dog. Being dominant, once lost, it cannot be produced unless reintroduced.
Black mask fawn is the next in the series. Recessive to brindle, but dominant over pied. Frenchies of this colour, mated together, can only produce black mask fawn and fawn pied. (Fawn can be categorised as being from the palest cream to deep mahogany).
Pied is the lowest denominator with the extreme version producing an almost white dog? The pied gene actually inhibits the ability of colour to express itself as opposed to being a true whole colour in its own right and this gene is actually for white spotting with various degrees of intensity providing different effect. Now with pied, the brindle dominant, fawn recessive rule still applies.
Because of this pied gene in the breed, varying degrees of white can be displayed on a brindle or fawn Frenchie. From just a small white spot, to Irish spotting pattern with chest, muzzle, forehead, belly, feet and tip of tail, possibly displaying white, in some or all of these areas, however because this pattern is able to be modified by the gene for complete body pigment and the piebald spotting gene, smaller or greater areas of white may be displayed.
There are four genes in this series in order of dominance.
Self. Completely pigmented body
Irish spotting, with definite located areas of white
Extreme white pied
These are the basic colour genes, which determine the possible colour of pups from certain colour matings.
Other genes exist in certain lines, which are not always of benefit to the colour of the Frenchie;
Progressive Greying of muzzle gene is dominant
Ticking gene creating flecks or spots on white and is dominant and undesirable. The recessive clear white coat is what is required.
Black dark pigment gene is dominant over recessive liver / brown.
Full pigmentation is dominant over the recessive lighter shades of coat.
An enigma exists with the American CREAM colour, as this defies the usual definitive colour outcomes of colour matings. It is possible that a number of different gene combinations can portray visually the same cream colour, but their genetic make up being different, causes different resulting colours in their off spring. i.e. cream / fawn / red / butterscotch.
It would appear that cream/ fawn (without mask) is due to a colour gene of a totally different series to that of the black mask fawn. Standing alone and not interacting with the fawn of the black mask series.
Hence to produce either recessive colour you must have two recessive genes of the same kind i.e. two BMF genes to produce black mask fawn and two cream/fawn genes to produce that also. Being a different series that do not interact, Cream/Fawns and BMFs can be produced in the same litter providing both parents carry the recessive gene for both colours. However pure Cream/Fawn X pure BMF will produce nothing but brindle as progeny only carry one of each colour gene and TWO of the same series are required to produce either colour. Cream and BMF suppress the brindle pattern being displayed, when in their double recessive form, hence only one of each allows brindle to manifest.
It should also be noted that American cream is also a dilute, possibly C ch and therefore does not always have the ability to produce jet black pigment as our black mask series does. This off black pigment, while dark, is a brownie black and not acceptable according to our standard. It is possible however for cream to have black pigment, when black mask fawn is carried recessively or it is of the E series of fawn and not the recessive e version.