Excerpts from 'The Inheritance of COAT COLOR in DOGS'

Clarence C. Little, Sc. D.

Published 1957

Scottish Terriers

Various shades of brindle, wheaten or black are the usual colors of this breed. The brindles may be any shade of red or gray as far as the lighter ground color is concerned. The darker shades are probably found in animals that are CC, the intermediate shade in the Cc^ch type, and the very pale shades in the C^chC^ch individuals. The same relative shades of wheaten are probably to be explained genetically in the same way.

Theoretically the blacks may be of either of two types. They probably are extremely dark or reduced brindles in which no easily distinguishable evidence of the pattern exists. Such blacks would breed like brindles.  Black could also occur as the result of mutation from a^u, the gene which is characteristic of brindles, to A⁸.  Blacks of this sort could carry brindle, being A⁸a^ue^bre^br, or they could be A⁸A⁸e^bre^br and breed true.

In the latter part of the nineteenth century and the early years of the twentieth the black-with-tan-points variety became less common; it has now largely disappeared from most of the strains being used to produce bench-show animals.

An instance of a mutation from black B to liver b was recorded in an Iowa kennel some forty years ago, and the writer saw two of the liver-brindle (bb) animals with light-yellow eyes and flesh-colored noses. Otherwise they were typical Scottish Terriers in conformation.  The writer has also observed a mutation from the ordinary solid-colored type S to piebald s^p in a carefully controlled mating in his father's kennel.

Light-yellow or cream and pure-white Scotties (formerly known as Roseneath Terriers) represent a wheaten type in which the gene C for full pigmentation has been replaced by the paling gene c^ch. The mutation is a rare one but has been observed by the writer in his father's kennels. Older dog books describe the relationship of creams and whites in a manner consistent with the above theory. 

Wheatens, like sables in other breeds, may be clear-colored or may show varying amounts of scattered dark pigment, especially on the back and sides. Usually this disappears with age.

Masks may well have been present at one time. They are favorably mentioned (Shaw, 1881). It is interesting to note that they are still found in Cairn Terriers, a breed which probably has common ancestors with the Scotty.

In Scottish Terriers the genes are as follows:

Definitions of the genes identified by Clarence Little in the above chart

A⁸ 'allows the distribution of dark pigment over the whole body surface'

a^u 'restricts markedly the areas of dark pigment and in its most complete expression produces a clear sable or tan-colored dog.'

a^t 'produces the bicolor varieties. All of these we shall describe as tan-points¹.'

B Black coat color

b alternative and recessive form of B, allows the reduced degree of pigment formation observed in the liver series of dogs.

C Full depth of pigmentation

c^ch 'chinchilla', reduces the red-yellow pigment, most notably seen in the golden brindles, dark tans or reds, has minimal impact on a B

D intensely/densely pigmented

e^br   Brindle

E 'allows the formation of dark (black or brown) pigment evenly over the whole coat'

E^m  Black masking

g

m

S

sp

t

¹ Dogs with this coat-color pattern have tan muzzles, feet, under surfaces of the tail, anal regions, etc. Because the dark part of the coat may be either black or liver, it is necessary to devise some term that will include both black and tan and liver and tan to show that they have the same genetic pattern gene. For the reason the term "tan-points" is used to include any manifestation of the pattern, no matter what the darker ground color may be.