Lucas Terrier Club

This article is by no means meant to be a comprehensive guide to the coat colours found in dogs generally, it specifically looks at the colours found in the Lucas terrier. Also, since I know many people find the whole subject of genetics one big yawn, I have tried to keep it as light as possible.

Even so, I think it is important that anyone reading an article on coat colour must have the most basic understanding of what the two main pigment types are in mammalian hair. These are 1) eumelanin which is black/dark brown and 2) phaeomelanin which is red/yellow.

Specialised cells in the hair follicles place the melanins (which are in a granular form) into the shaft of the growing hair. Not all hairs are the same colour and the reason for this is that there may be differences in the synthesis of the pigment or where the pigment in deposited in the hair. The hair shafts can contain a variety of colours (or even colourless pigment granules), including yellow, red, grey, brown and black, so each hair, dependent on the kind and amount of pigment plus the amount of granules, may vary in shade from its neighbour. The variation can also be seen to change along the shaft of one hair.

The pattern of pigment in hairs and how it is seen across the dog is controlled by three groups of genes and these are the agouti and extension loci with several dilution loci affecting, or controlling, the colour of the eumelanin and phaeomelanin and the white spotting loci controlling unpigmented - white - parts of the body.

The colour in the Lucas comes from the Agouti gene. The alleles within this gene series are as follows:-

Ay - Dominant yellow - this allele produces a dog which is predominantly tan (due to phaeomelanin) sometimes with hairs that are black at the tips or the coat is interspersed with black hairs. This is usually described as 'sable' I have never seen a tan (or tan marked) Lucas puppy that did not have a black overlay to the tan, though this does disappear to a large extent in the adult coat.

The black overlay on a sable can clearly be seen on this puppy

asa -saddle and tan and at - tanpoint - saddle pattern appears to lie somewhere between sable and tanpoint. Saddle certainly acts as though it is recessive to sable and dominant to tanpoint, but may well be caused by a gene at another locus that modifies the normal tanpoint pattern. The saddle pattern is also seen in the German Shepherd and Airedale terrier - not to mention the Norfolk terrier, which is one of the Lucas terrier's parent breeds. Saddle and tan puppies look no different from tanpoint puppies at birth - like tiny Rottweilers. However, as the dog matures the tan creeps up the face and legs leaving only a dark saddle on the dog's back.

A newborn saddle and tan puppy can be seen second from left with her sable litter mates.

This is the same saddle and tan puppy as above at approximately 8 weeks.

Look at the amount of tan on Tango's head, front and up her rear leg. This is typical of saddle and tans

This bitch's coat pattern is described as tanpoint.

Tanpoints retain the pattern they were born with and, generally, the black in the coat doesn't lighten as it almost invariably does in saddle and tans. This pattern is uncommon in comparison to saddle and tan.

B - Brown series - there are only two alleles in this series, B and b. B, in single (Bb) or double (BB) dose means the dog will have black pigment. A bb dog has brown pigment, usually described as liver or chocolate, wherever the dog would otherwise have been black. I have never seen a liver Lucas terrier and believe that all are BB.

C - Albino series - C allows for full expression of whatever color is allowed by other genes. Most dogs are CC and I have no reason to believe that the Lucas is any different.

D - the Dilution series - another fairly simple series with D being dominant and allowing full pigmentation and d which is the recessive and dilutes both eumelanin and phaeomelanin pigment. I am confident in stating that Lucas terriers are DD.

E - Normal extension of black - this allows the A-series alleles to show through. All Lucas terriers will be, in my opinion, EE at this locus. I have never seen a tan Lucas or one with tan markings where the tan did not have a sable overlay and this would not be the case if some Lucas terriers were homozygous ee as the homoyzgosity strips all black out of the coat.

G - Greying series - there are perhaps more than the two alleles (G - greying and g - non greying) recognised by Little in this series. Or, it could be that there is more interaction between this and the other gene series than is understood at this time. The effects of G in a single or double dose is that coloured hair is replaced by non-coloured hair early on in the dog's life (it is sometimes also referred to as the Paling gene which may give a clearer picture of what is going on). The fading starts very early in the Lucas terrier and the black in the saddle and tans can be seen to begin to turn silvery-blue from as young as 6 weeks and gradually the rich red tan is replaced by a more biscuity shade. It does seem in some cases to continue right through the dog's life time.

Saddle and tan showing the effects of greying/paling

M - merle series. The Lucas is mm (non-merle)

T - Ticking series. The Lucas is T (ticked) and carries the recessive t (non-ticked)

S - White spotting series. This is a rather unsatisfactorily explored series and there seems to be some fuzziness about how a dog moves from one descriptor to another, that is to say, piebald Lucas terriers bred together often produce extreme white piebald progeny.

S - Solid color - this is the normal gene in breeds without white markings, such as the Norfolk, which, of course, is one of the parent breeds used to produce Lucas terriers.

Solid dog, no white on him whatsoever

si - Irish spotting - this is where the white is confined to the nose, toes, tummy, bib, tail tip if the dog is not docked and sometimes the back of the neck - this colour pattern is most often found in Norfolk/Sealyham hybrids. In the Lucas it is likely that this colour pattern is a combination of S and sp which mimics Irish spotting. Sometimes once the adult coat comes in it is difficult to see the white areas.

Saddle and tan with white bib

sp - Piebald -piebald and extreme white patterns overlap in a sort of fuzzy way, which makes the phenotype of some piebalds difficult to identify with any degree of certainty . As a general rule of thumb a piebald has more than 50% white but the splotches are quite large (sometimes described as 'slabs' or 'plating') in comparison to those found on the extreme white. The white on a piebald, unlike that on an Irish spotted will be found on the body behind the withers.

Piebald dog with ticking

sw - Extreme white - these range from colour-headed whites which may also have a few coloured spots on the body, especially near the tail, to completely white dogs. There is some evidence that a lack of colour on the head may be connected to deafness and the breeding together of extreme white Lucas terriers is not recommended. Of course the other Lucas parent breed (the Sealyham) is an extreme white breed.

Colour-headed white

Extreme white

All of the above colours are acceptable, as is white with black and white with both black and tan markings, though they are very much in the minority. However, all, or predominantly, black dogs crop up very occasionally - I have known of two here and one in the USA - this is not considered to be correct.

Below is a photograph of a dog with undesirable colour. This is possibly caused by the (dominant) black locus - K

This is a relatively new addition to the traditional models of dog colour genetics. K codes for both dominant black and brindle in decreasing order of dominance: K=dominant black, kbr=brindle, k='normal'. So a dog that is KK or Kkbr is dominant black, kbrkbr or kbrk is brindled, and kk is whatever is determined at the A and E locii. Lucas terriers are never brindle so we can ignore this allele

It appears that three loci (E, K and A) act together and affects Lucas colouring as follows:

Lucas terriers are always EE and if it is K- at the K locus its coat will be entirely eumelanin based (dominant black);

If the Lucas is EE at the E locus, and kk at the K locus, the distribution of eumelanin and phaeomelanin will be determined solely by the Agouti alleles present, so would be tan, saddle and tan or tanpoint, or predominantly white with tan, black, or black and tan markings.

It would appear that some Sealyhams are dominant black dogs but the colour is masked by white from the sw allele. In some Lucas litters the dominant black, however, is given expression.