THE TICKING GENE

Ticking is flecks or spots of colour on white areas. It can occur on any white area on a dog, so long as the white is "proper" white ( i.e. so long as it's caused by the white spotting series and not by the chinchilla gene). If a dog has the ticking gene but doesn't have any white areas, there will be no visible effect.

The gene which codes for ticking has not been found yet, but it is thought to be dominant. It has been assigned its own locus - T - and there are generally thought be two genes on that locus. T is the dominant ticking gene, and t is the recessive clear white gene. A tt dog will have clear white with no ticking.

Ticking amount varies greatly between dogs, and this can be partly explained by the idea of incomplete dominance. If the ticking gene (T) displays incomplete dominance over the clear white gene (t), then a TT dog would have heavy ticking and a Tt dog would have lighter ticking. This doesn't seem to account for all the variation found, however, so there may be other modifiers which affect ticking amount.

Generally, ticking is heaviest on the legs and the muzzle. If a dog has only a small amount of ticking, it will appear in these areas before appearing anywhere else (although occasionally, in dogs with very tiny flecks, they may be evenly distributed over the body). Sometimes, long fur on the body can distort and hide ticking spots, whereas fur on the legs and muzzle is generally short, so this can make the difference between the ticking on the body and on the legs even more noticeable.

The colour of ticking corresponds to the colour that the area would have been if there wasn't any white there. For example, a black-and-tan dog with white markings and ticking would have black ticking on its body and tan ticking on its legs, chest and muzzle, where it would be tan if it didn't have white. The Canaan Dog below shows this well, and scroll down to the English Setter picture to see another example.

Roan is a pattern which produces heavily mottled white areas. Often only a small amount of scattered white is visible.

The Australian Cattle Dog above is an extreme example of roan. It is genetically a black-and-tan, so the roaning is black on the body and tan on the points. The whole dog would be white if it didn't have roaning. The overall effect on the black areas is similar to the "salt-and-pepper" colour found on Schnauzers, except if you got a close-up look at the hairs, you'd be able to see that they're not banded like the hairs on Schnauzers are. The Basset Bleus in the other photo show what roan looks like on short-haired dogs. They show that roan actually consists of lots of spots, packed very densely to cover most of the white. This has led some people to believe that roan is, in fact, just very heavy ticking. However, others believe that it is controlled by a separate gene.

Personally, I think it's possible that there are two genes - one which causes the large ticking spots seen on breeds such as Springer Spaniels, and another which causes much smaller ticks and flecks. Either one has the potential to be heavy enough to become roan, but the resulting roan looks a little different. The larger spots produce roan like the Basset Bleus, and the smaller flecks produce roan like the Australian Cattle Dog, where, because the flecks are so small, it's hard to distinguish any sort of pattern. Of course, these two types of ticking/roan could just as easily be caused by modifiers rather than completely separate genes.

The English Setter above exemplifies the type of ticking with larger spots, and the Bracco shows the type with smaller flecks. The Setter photo was taken by Kenzie.

These three Cocker Spaniels show how ticking seems to become roan. The first dog has medium ticking, the second heavy ticking, and the third roan.

Black dogs with roaning often appear a greyish colour, and are commonly called "blue roans". The dogs above are blue roans. Just like with "blue merles", these dogs are called "blue" but aren't actually genetically blue. The term "blue" is usually used to refer to black dogs with the dilute gene (dd), which dilutes the coat and nose to grey and the eyes to amber, but neither blue roans nor blue merles have this gene.

The dogs above are liver roans. They are black roans with the liver gene, which turns their patches and their roaning to brown.

Dogs with ticking or roan are generally born white. The ticking/roaning develops as the dog grows. This can be rather dramatic, as in the Australian Cattle Dog. There is a popular myth that Australian Cattle Dogs are born white because of their Dalmatian ancestry. In fact, they are born white simply because they have the extreme white spotting pattern with roaned white areas. The roaning takes a while to develop, but the extreme white spotting is there from birth, hence the puppies are completely or almost completely white.

DALMATIAN SPOTS

Dalmatian spots puzzled geneticists for a long time. They are completely unique to the breed and do not occur anywhere else in the dog world. Contrary to looks, Dalmatian spots and the harlequin pattern in Great Danes are not related.

It is now fairly certain that Dalmatian spots are in fact a modified form of ticking. If you compare the Dalmatian above to the English Setter up in the section about roan, you'll see quite a few similarities. The Setter also has quite round and distinct spots, although they're distorted a little by the long fur. If the fur was shaved, the Setter would probably look very similar indeed to a Dalmatian.
There are, however, a few differences between Dalmatian spots and ticking. One of the main ones is that spots are often more sparse on a Dalmatian, bigger, and do not get more dense on the legs and muzzle. These are all probably to do with the modifier.

As well as the obvious similarity in looks between a dog with ticking and a Dalmatian, there are a few other things which indicate that spots are modified ticking:
- Dalmatians are born white and develop their spots later on.
- Dalis occasionally have patches on their head and/or body. These suggest that they have the extreme white pattern, meaning that the spots can't be caused by any of the white genes. The high rate of deafness amongst Dalis also supports this (extreme white is sometimes associated with deafness, as in white Boxers).
- Dalmatian crossbreeds are often ticked and never, as far as I am aware, spotted. This suggests that there is a recessive modifier behind Dalmatian ticking (so the Dalmatian parent passes down one copy of the modifier, but unless it's bred to another Dalmatian, there will never be another copy of the modifier, so it cannot be expressed).
- Sometimes Dalis are born which display some ticking or roaning (effectively "muddying" the base white). This is probably caused by a slight mutation or error in the modifier, stopping it from working completely.

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