ee-Red... and genes

The red Border Collie, like the chestnut horse, is the result of a recessive gene pair. In the case of the dogs, the dominant (black) is called E, and the recessive (red) is called e. A black dog may be either EE or Ee; the red dog is always ee. Two black dogs may have red puppies if both of them are Ee; the e can come from each parent to produce ee in the pups. Statistically, one out of four pups with such a cross will be red. If either parent is EE, though, the combination can't produce red pups. If both parents are red, ee, then all their puppies will be red; there is no E available from either parent to make a black pup.

The end product of most genes is some sort of biochemical substance. In the red color, the chemical is a pigment called eumelanin. This is one of a group of pigments, the melanins, which cause color in animal skin, hair, and feathers. It is responsible for very dark brown or black color. All Border Collies have in their hair a red version of melanin, called phaeomelanin. In the black dogs, the black eumelanin covers the appearance of the red. If you've ever looked closely at your black dog in bright light after he has spent a lot of time in the sun, you will see a faint red glow to his hair. The eumelanin has been bleached by the sun, and the red color is showing through, however slightly.

Only the dominant version of the color gene results in eumelanin production; if the dog has two copies of the recessive version, he will have no eumelanin. His hair will contain only the red pigment, and anywhere that he would otherwise have been black, he will instead be red. This means he may have the same variety of white markings as any black Border Collie; he may be tri-color, with lighter brown markings in all the usual places; he may even be a red merle instead of a blue merle. His nose and toe pads, which would be black on a black dog, are red-brown.

The red gene is present in some of our favorite breeding lines. The first recorded red Border Collie was a bitch named Wylie, grandmother of the famous Dickson's Hemp (153). The recessive gene passed through the generations to J. M. Wilson's Cap (3036) who appears in the pedigree of Wiston Cap at least 16 times! Wiston Cap carried the red gene and passed it to many of his sons and daughters. Our current Border Collies tend to have many crosses of Wiston Cap in their background; each one increases the chances of receiving that e gene. Crosses on both sides of the family, likewise, increase the chances of a double dose and the appearance of more and more red dogs.

Unlike most simple genetic traits, however, good (or bad) hips don't result from a single pair of genes. With a single pair, like the "red" genes, the probability of each genetic combination in the next generation is easy to measure. We know exactly how many red pups, statistically, to expect from any combination. With hip dysplasia, on the other hand, we have no idea what to expect in a litter of pups, even if we have x-rayed both parents.

Instinct and behavior, like hips, are affected by a large number of genes; some may be recessive like the e; some may be dominant like the E. The problem is that we don't know how to identify any of them, and we have no idea how many there are. If we had some kind of behavioral measurements on all the members of hundreds of litters and their parents and offspring, we could make a start. We aren't even close. We have no real measurements at all; our assessment of herding ability is subjective, and deals with the whole dog and his ability to get the job done.

Studies by Scott and Fuller on spaniels revealed the genes involved in the behavior known as "crouch"; the crouch itself is controlled by two major genes, with the crouch (or sit) dominant over the stand. The quiet attitude was also controlled by two genes, with the quiet behavior recessive to the more active. The whole pattern of quietly crouching, then, results from four genes altogether. The number of different genetic combinations that can be formed from 4 (2-allele) genes is 81! If the parents are heterozygous for all four of these genes, any of these genetic combinations is possible in the same litter.

What does all this mean to the Border Collie? Imagine, if that simple quiet crouch behind the sheep depends on 4 separate genes, what must be involved in the entire collection of herding behavior: eye, balance, power, biddability, etc. And what must the chances be of accidentally combining the right factors to remake a herding dog, if those combinations are ever lost?

The complexity of the genetics of behavior is probably not a surprise, but it is the basis of the entire argument that the performance dog must be bred for performance at every generation. The more genes are involved, the more different combinations are possible, the more easily they become separated and lost.

If the dogs selected for breeding for conformation are not the ones with the best herding genes, the population will inevitably drift away from the wonderful performance combinations that have been selected in the breed for so many generations.

Because the extremely complex instinct that makes up the working dog is not fixed in the population, constant selection is needed, at every generation, to maintain the best combinations. Any relaxation of this pressure will result in the increase in numbers of those dogs which have less than ideal genetic combinations. Breeding for any other purpose without also selecting for truly high quality working genes will inevitably result in the dilution of the working instinct within the breed.
Genes may have more than two different alleles (there are 160 different alleles of the blood group gene, B, in cattle). The number of possible genetic combinations as we increase both the number of possible alleles and the number of genes rises abruptly. If we are dealing with, say 6 traits (see above), each with an average of only two gene loci involved, that is 12 genes; if they have only 2 or 3 possible alleles:

"With even moderately small numbers of polymorphic genes, the number of genotypes that can be produced by recombination is likely to be greater than the existing number of individuals in the species." (V. Grant, in The Origin of Adaptations).

If we are already trying to maintain some genetic equilibrium with all these possibilities, consider the additional burden of selecting at the same time for color, ear type, body size, coat quality, eye color, head shape, etc., to fit some arbitrary standard of appearance. The number of different genetic types becomes astronomical. The number of dogs that can fit all these separate standards for all these separate genes is, as Verne Grant stated it, probably less than one in the whole breed! The number that will come close is still very small. This is particularly true within a breed like the Border Collie where there is no genetic uniformity in appearance to begin with.

copied from: http://www.bordercollie.org