15

The Emergence of Modern Breeds

By the middle of the nineteenth century, dog breeds became formalised, first by the Kennel Club and shortly after by its North American equivalent, the American Kennel Club (AKC), formed in 1887 from the amalgamation of US and Canadian breed clubs. As well as coordinating the increasingly popular dog shows and field trials, both clubs were concerned about maintaining breed purity. The AKC stated as much in the aims set out in its prospectus: ‘to do everything to advance the study, breeding, exhibiting, running and maintenance of purity of thoroughbred dogs.’ Both organisations have worked closely together from the outset and, as well as organising dog shows and a host of other activities, both maintain breed registries which are updated on a regular basis. New registrations are accepted only if both parents are of the same breed. This requirement brings its own complications, as we will see.

Both clubs publish registration statistics. The Kennel Club registers 250,000 new dogs every year and the AKC figure is approaching 1 million. At the most recent count the AKC registry recognised 202 different breeds, while the Kennel Club total is slightly higher, at 218. The two clubs also assign breeds to one of a small number of descriptive classes: gun-dog, hound, pastoral, terrier, toy, utility and working in the UK, and very similar classes in the USA. There are kennel clubs in almost every country and most are affiliated to the Fédération Cynologique Internationale, an umbrella body formed in 1911 with headquarters in Belgium. Their stated remit is equally explicit: ‘… to encourage and promote breeding and use of purebred dogs whose functional health and physical features meet the standard set for each respective breed and which are capable of working and accomplishing functions in accordance with the specific characteristics of their breed.’

Kennel Club breed classes

Class	Typical breeds
Gun-dog	Retrievers, Spaniels, Pointers, Setters
Hound	Scent: Beagle, Bloodhound
	Sight: Whippet, Greyhound
Pastoral	Collie, Sheepdog, Samoyed
Terrier	Highland, Jack Russell
Toy	Chihuahua, Pomeranian
Utility	Bulldog, Dalmatian, Akita, Poodle
Working	Boxer, Great Dane, St Bernard

New breeds are added to the list from time to time and there are strict criteria for their acceptance. Every breed has an agreed written standard to which pedigree dogs must conform. These are mainly concerned with their appearance, with temperament coming a distant second. They are policed by dog show judges who use the breed standard as a yardstick for scoring competitors.

This is a typical Kennel Club breed standard, in this case for the Beagle:

General Appearance

A sturdy, compactly built hound, conveying the impression of quality without coarseness.

Characteristics

A merry hound whose essential function is to hunt, primarily hare, by following a scent. Bold, with great activity, stamina and determination. Alert, intelligent and of even temperament.

Temperament

Amiable and alert, showing no aggression or timidity.

Head and Skull

Fair length, powerful without being coarse, finer in the bitch, free from frown and wrinkle. Skull slightly domed, moderately wide, with slight peak. Stop well defined and dividing length, between occiput and tip of nose, as equally as possible. Muzzle not snipy, lips reasonably well flewed. Nose broad, preferably black, but less pigmentation permissible in lighter coloured hounds. Nostrils wide.

Eyes

Dark brown or hazel, fairly large, not deep set or prominent, set well apart with mild, appealing expression.

Ears

Long, with rounded tip, reaching nearly to end of nose when drawn out. Set on low, fine in texture and hanging gracefully close to cheeks.

Mouth

The jaws should be strong, with a perfect, regular and complete scissor bite, i.e. upper teeth closely overlapping lower teeth and set square to the jaws.

Neck

Sufficiently long to enable hound to come down easily to scent, slightly arched and showing little dewlap.

Forequarters

Shoulders well laid back, not loaded. Forelegs straight and upright well under the hound, good substance, and round in bone, not tapering off to feet. Pasterns short. Elbows firm, turning neither in nor out. Height to elbow about half height at withers.

Body

Topline straight and level. Chest let down to below elbow. Ribs well sprung and extending well back. Short in the couplings but well balanced. Loins powerful and supple, without excessive tuck-up.

Hindquarters

Muscular thighs. Stifles well bent. Hocks firm, well let down and parallel to each other.

Feet

Tight and firm. Well knuckled up and strongly padded. Not hare-footed. Nails short.

Tail

Sturdy, moderately long. Set on high, carried gaily but not curled over back or inclined forward from root. Well covered with hair, especially on underside.

Gait/Movement

Back level, firm with no indication of roll. Stride free, long-reaching in front and straight without high action; hindlegs showing drive. Should not move close behind nor paddle nor plait in front.

Coat

Short, dense and weatherproof.

Colour

Tricolour (black, tan and white); blue, white and tan; badger pied; hare pied; lemon pied; lemon and white; red and white; tan and white; black and white; all white. With the exception of all white, all the above-mentioned colours can be found as mottle. No other colours are permissible. Tip of stern white.

Size

Desirable minimum height at withers: 33 cms (13 ins). Desirable maximum height at withers: 40 cms (16 ins).

In summary, this is a pretty stringent set of criteria to which breeders, if they show their dogs, try hard to comply.

From a genetic point of view, modern pedigree breeds conforming to Kennel Club rules are the canine equivalent of the desert island we introduced back in Chapter 5 from which no one leaves and at which no one arrives. Once on the island, they are completely cut off from all other dogs. They can only breed with each other and this is the perfect scenario for inbreeding. Strange things can happen with inbreeding in any species, and to understand them we need to go back to the basic biology. I will borrow some of my examples from human genetics, as we understand these very well indeed.

The problems of inbreeding all stem from a fundamental aspect of mammalian biology. They are a consequence of having not one but two pairs of each chromosome. This is the case for all mammals including, of course, dogs and humans. The genes that we and all mammalian species need in order to live and reproduce are located on these chromosomes. One of each pair comes from the mother and one comes from the father. Thus we have a paternal copy and a maternal copy of each gene. Different species have different numbers of chromosome pairs, twenty-three in humans and thirty-nine in dogs. The number is relatively unimportant. It is the genes on the chromosomes which really count. Ideally we, and dogs, need all the genes from both parents to function properly, but we can usually get by with one, as long as it is in good condition. Under these circumstances the genes on the other chromosome act as back-up.

A harmful mutation in a gene on one of the chromosome pairs is usually offset by the normal, fully functional gene on the other member of the pair. However, if the ‘normal’ chromosome cannot compensate for the faulty mutant, then the individual will suffer from a genetic disease which will, almost always, reduce the prospects for the individual to have offspring. In humans this usually means that affected individuals have fewer children, while in dogs the mutants will not be chosen for breeding and may be euthanised, unless the mutation happens to be a Darwinian ‘sport’ with exotic appeal.

When the ‘normal’ chromosome is able to compensate fully for its damaged partner, the individual, human or dog, will usually show no outward sign of the problem that lurks within. Such an individual is known as a ‘carrier’. It is a problem that only surfaces in later generations, if two carriers meet and breed. The simple rules of genetics dictate that when this occurs, one half of pregnancies will be carriers like their parents, one quarter will have two ‘normal’ chromosomes but in one quarter both chromosomes will carry the mutant gene. Without a normal gene to compensate for the loss, the individual will show symptoms, whatever they happen to be. The disease is then said to be recessive.

Within human communities, genetic diseases which only show when both parents are carriers have been known for a long time and are the main reason for restrictions on the marriage of biologically close relatives that are widely taught by many religions. By definition, close blood relatives share a common ancestor in the recent past. Full siblings share both parents as ancestors, first cousins have the same grandparent and so on. Taking the last example, if the shared grandparent is a carrier of a genetic disease, he or she would be completely normal and almost certainly be unaware of being a carrier. However, the mutant gene may be passed on to his or her descendants, again following the simple rules of inheritance. The parents of the two cousins, who are siblings, each have a 50 per cent chance of inheriting the mutant gene from whichever of their parents was the carrier. That gives them a 25 per cent chance that both are carriers. If they have children, every pregnancy will have a one quarter chance of inheriting the mutant gene from both parents. With a double dose of the damaged gene, and lacking the back-up of the normal counterpart, the child will exhibit all the symptoms, sometimes with devastating consequences.

The reason that this type of inherited disease is rare in outbred communities is that, though all humans are symptomless carriers for around fifty serious genetic diseases, the chances of their descendants marrying one another is small. However, some genetic disorders are far from rare. The commonest human recessive disease in Europe is cystic fibrosis, which is usually caused by a single mutation in a protein within the cell membrane that regulates the passage of chloride ions in and out of the cell. The unfortunate cystic fibrosis patients produce a much stickier mucus than normal and this builds up in the lungs. Although tedious daily physio-therapy can help clear the mucus, there is a greatly increased risk of lung infections, and most cystic fibrosis patients die of pneumonia before they reach forty.

The proportion of cystic fibrosis carriers in Europe is surprisingly high, at one in twenty. The reasons for this are extremely interesting, and we will deal with them a little later. But, again following the simple rules of genetics, if the carrier rate is one in twenty, the chances in an outbred community of two carriers becoming parents is 1/20 x 1/20, that is 1/400. Under these circumstances each pregnancy has a one in four chance of inheriting two copies of the mutant gene, giving an overall prevalence of cystic fibrosis of 1/1600.

If, however, the two parents are descended from a recent shared carrier ancestor, the incidence of the disease increases dramatically. This is especially notable in some closed religious communities, like the Old Order Amish in Lancaster County, Pennsylvania. The ancestors of present-day Amish, and the closely associated Mennonites, emigrated from Germany in the early eighteenth century. They are certainly prolific and, by 2012, their numbers had grown to almost a quarter of a million. The Amish have an unusual way of life, eschewing modern amenities like cars, telephones and electricity. They drive around in horse-drawn carriages, and if you have ever been taken for a ride around Central Park in New York, the carriage was probably made by an Amish craftsman.

I mention the Amish because in many ways, from a genetic point of view, they resemble the closed breeding communities of the pedigree dog. The Amish only reproduce within their own communities, just as pedigree dogs must do if breeders want their litters to be registered. One might imagine that the incidence of genetic disease in the inbred Amish would be much higher than in the general outbred population, but this is not so. They do, however, have higher rates of particular genetic conditions, some of them serious. One of these is SCID or severe combined immunodeficiency disease, also known colloquially as ‘bubble boy syndrome’. SCID patients have such a weakened immune system that they must be completely isolated from all sources of infection until they are old enough to receive a bone marrow transplant. SCID among the Amish is caused by a mutation on chromosome 15 called IL7R, which is a receptor for interleukin, a protein concerned with inter-cellular communication. Mutations in other genes also cause SCID but not in the Amish, so it is only the specific IL7R mutation that has been inherited from the shared carrier ancestor of affected Amish children. It was almost certainly present in one of the two hundred original founders of the Old Order Amish who emigrated from Germany. It remains hidden within the population until exposed in a double-dose SCID patient.

Similarly, pedigree dogs, as we have seen, come from a genetically limited pool of founder ancestors. If one of their number is a carrier of a mutant gene it is in the gene pool and will lie dormant until it shows itself when two mutant genes are combined within a single individual. However, if conversely there are no carriers among the founding dogs, the whole pedigree will be free of the disease.

Theoretically, now that we can identify the precise mutation, the Amish could all be tested to see who was a SCID carrier and avoid the situation altogether by making sure two carriers did not marry or at least did not have children. However, their religious views forbid them from participating in preventative genetic testing, instead accepting the diseases as ‘God’s will’. Other human communities have found themselves in a similar position but have shown a determination to do something about it.

For example, another fatal inherited neurological disorder, Tay-Sachs disease, affects the Ashkenazi Jewish community of New York and elsewhere. They are not quite such a completely closed breeding community as the Amish but they do show a high degree of inbreeding as a result of their tightly knit East European origins. They used to have a high rate of Tay-Sachs disease for the same underlying reason as the Amish, again because inbreeding often brought together two carrier parents. The Tay-Sachs mutation is located on chromosome 15 in a gene called HEXA. Identifying the genetic mutation means that carriers can be identified by a simple DNA test. Unlike the Amish, the Ashkenazi community have enthusiastically embraced DNA-based carrier screening. Carriers are discouraged from marrying other carriers and, as a result, the incidence of the disease has dropped to zero. There are now more Tay-Sachs babies born to non-Jews, who are at very low risk so aren’t screened for carriers.

There are strenuous efforts among pedigree dog breeders and organisations like the Kennel Club to emulate the success of the Ashkenazi Jews in eliminating Tay-Sachs disease by using DNA tests to screen pedigree dogs to reveal carriers of diseases common to their breed and discourage them from breeding. This will quickly reduce the frequency of the disorder. In time, the incidence of carriers within the pedigree breed will go down and, with sufficient effort, could be eliminated altogether. From this point onwards the breed would be free from the disease.

In the UK the leading testing lab, the Kennel Club-sponsored Animal Health Trust (AHT), has developed tests for twenty-two different inherited disorders present in sixty-five different dog breeds. Other centres have also developed DNA tests for carriers and breed identification, of which more later. The same mutation, and the same disease, can be present in different breeds because some of the dogs that were used to create the breeds were already carriers. The Trust laboratories are near Newmarket in Suffolk and boast an impressive track record. They have DNA tested over 85,000 dogs from around 50 different countries for the mutant genes responsible for the 22 recessive disorders and identified nearly 10,000 carriers.

Each of these mutations, in common with all genetic mutations, has arisen spontaneously. Where the mutation and the disease are found in only one breed, the likelihood is that they arose after the breed was closed. However, as I mentioned above, when a specific mutation and its associated disease occur in more than one breed, the chances are that the mutation arose before the breed was closed to outsiders.

I arranged a visit to the AHT labs and found out more about their activities and a lot more besides, which we will come to in Chapter 20.