What disqualifying (non-standard) colors are most common in Aussies?
Too much white is most common, then dilute, closely followed by yellow. Yellow and dilute are both recessive, so they have continued to lurk in the breed gene pool, showing up only when two carriers happen to be bred to each other. The basic “Irish” pattern of white markings typical of Aussies is probably caused by a single gene but modified one way or the other by additional genes or regulatory DNA. The genetic cause of mismarks (dogs with too much white for the breed standard) is not clear at this point though one gene, referred to as S (spotting) may vary the extent of markings somewhat.
What is a mismark?
A dog with white in places the breed standard does not allow it. A white body splash would be a good example.
Have mismarked Aussies become more frequent than they were years ago?
Possibly, though it is difficult to know for sure. Very early in breed history dogs with what we would now consider too much white were not unusual. However, in the late 1970s when a standard was developed that is largely the same as those in use today, the distribution of white markings became fairly well-defined. The limitations were aimed at mismarks and intended to discourage people from producing double merles, but it also had the effect of shifting selection more strongly against mismarks.
If that is so, why do we see so many mismarked dogs today?
Show ring fashion rewards flashy white markings, which encourages pushing the limits, and stockdog breeders don’t necessarily care because the markings don’t affect a dog’s ability to handle stock. Given that, there will probably always be some level of mismarks though extremes such as piebald dogs have become far less frequent.
What gene causes dilution?
The D locus (dilution, genetic designation MLPH).
Does D also cause dilution spots?
No. Dilution spots, grey and often rusty or dull areas in a merle pattern, are related specifically to merle with the genetic cause unknown at this time. D dilutes all black or liver pigment, including all shades of a merle coat. A dilute blue merle would have grey or slate blue dark spots instead of black and the lighter areas would be pale silver. A red merle with dd would experience the same effect, but it would be less visually obvious. Because of the wide range of color intensity in red merles it is possible tht some dilute red merles are not recognized as such.
Does D cause other colors?
D causes a dramatic lessening of black or red (liver) pigment but there are clearly other things that can affect density of pigment. The exact shade of color produced by D may vary somewhat. For example, red Aussies may be deep chocolate to chestnut to orange and red dilute can vary accordingly. Blue Dobermans and Great Danes are dilute blacks; a Weimeraner is a dilute red. Nose and other skin pigment will also be lighter in color but tan markings will not be affected. The color of the eye will often be a bit lighter in dilutes than in non-dilutes in the same litter.
How many versions does D (MLPH) have?
Two – non-dilute and dilute, with dilute being recessive.
Is dilute acceptable in Aussies?
How is dilute inherited?
It is recessive. A dog with two non-dilute versions of D will not be dilute nor can it produce dilute. A dog with one non-dilute and one dilute version will carry dilute. Dogs with two dilute versions are dilute.
Is this the only type of Dilute in Aussies?
No. The researcher who identified MLPH dilute in Aussies also received samples from dilute dogs that did not have this mutation. Therefore there are other ways dilute may be inherited though they also likely recessive. Sometimes Aussie puppies will be born dilute but as they mature their coats darken until they can’t be distinguished from normally colored Aussies. This is not typical of the D locus, which gives the same color from birth onward.
What gene causes yellow color?
The E locus (extension, genetic designation MC1r).
Does E cause other colors or patterns?
Yes. It causes facial masks and the grizzle pattern in Salukis (called “domino” in Afghan Hounds.)
How many versions does E (MC1r) have?
Four: Mask, grizzle, black (actually whatever color other genes determine), and yellow in that order of dominance.
Are the E (MC1r) colors and patterns acceptable in Aussies?
“Black” is acceptable and mask only affects tan pigment so might reduce or eliminate tan points on the face. Grizzle doesn’t occur in Aussies but wouldn’t be acceptable if it did and yellow is not acceptable. Since yellow can obscure merle patterning to the point you cannot tell the dog is merle it isn’t a color that would be advisable in Aussies. Yellow dogs will not have tan markings but E does not interfere with white markings.
How are the E colors inherited?
Dogs with two copies of the mask version, or one copy of mask and any of the other versions will have a mask with the rest of the dog (save any white areas) yellow to reddish or possibly sable (depending on the versions of A it has.)
– Dogs with two copies of the grizzle version or one copy plus a copy of the black or yellow versions will be grizzle.
– A dog with two copies of the black version or one black and one yellow will be whatever color other genes determine.
– A dog with two copies of the yellow version will be yellow, though actual shade can range from pale yellow to deep red-gold. Yellow Aussies are usually a medium-gold shade.
What determines nose color in yellow dogs?
The B and D genes. The nose will be black or liver depending on what versions of B the dog has. If the dog also has two recessive copies of D the nose may be slate blue or a pale, even pinkish, brown.