Can you tell how inbred your pups are by counting the number of times individual dogs are repeated in the pedigree?
By Ralph Gillum, BraceBeagling Columnist
April 23, 2005

A five generation pedigree contains a possible sixty-two different dogs with each having its own unique genetic make-up. At first appearance, it would seem that if some dogs are repeated in the pedigree, that would indicate a doubling of their genetic influence. It is true that the more dogs you have repeated, the fewer the number of individual dogs you will have in the pedigree and therefore the higher the degree of inbreeding. However, it is a little more complicated than that, as the heredity material does not pass on down through the pedigree in equal proportions.

The thing to remember here is that the pedigree only shows the pup’s ancestors. It does not necessarily show the genetic or biological relationship between the dogs in the pedigree or their genetic relationship to the litter of pups! While it is true that every pup receives fifty percent of its heritage from each parent, the belief that each grandparent contributes twenty-five percent and each great-grandparent twelve and one-half percent and so on is simply not the case. In theory, any one grandparent could have contributed as much as fifty percent or as little as nothing to any one pup in the litter! So, while there are many ancestors listed in the pedigree, the pups may have inherited most of their traits from relatively few of them.

The relationship between two dogs is determined by the similarity of their genes. For example, a full sister can be more closely related genetically to one littermate then to another if they share more of the same genes. When considering this, it becomes apparent that simply counting the number of times individual dogs appears in the pedigree will not necessarily indicate the degree of influence they had on their offspring, i.e. their degree of inbreeding. Therefore, you need another way to evaluate the influence of dogs that are repeated in a pedigree. If there are dogs that are repeated, we can assume that some degree of inbreeding has occurred. However, the degree of inbreeding can best be detected by how closely the offspring resembles the ancestor repeated in the pedigree.

The true value of a pedigree is that each ancestor is listed so that you have the opportunity to discover their genetic make-up and to determine the portion of their genetic material they passed on to succeeding generations. Because some traits are recessive, this genetic material cannot always be seen when evaluating their looks and running actions. That they possess the genes for these recessive traits only becomes apparent when the traits appear in their offspring.

One way to evaluate the degree of inbreeding in a pedigree is the Past to the Present approach. First, locate and indicate by highlighting with a magic marker, all dogs that appear more than once in the pedigree. Next, look at each of the doubled up dog’s grand offspring listed in the pedigree. For all grand offspring, try to determine the extent to which each resembled the doubled up grandparent. The more closely they resemble their doubled up grandparent, the more of his/her genes were passed on to them. Since the inheritance from each grandparent is usually unequal, this will give a much more accurate picture of their actual influence than just looking at the number of times they appear in the pedigree.

The Present to the Past is a similar approach that is perhaps a little easier to visualize.
In this method you start with the pup or dog and look at all its ancestors. If the way your dogs run is your main interest, you may want to just consider running traits. Looking over the entire pedigree, highlight with your magic marker any dog that had a running style similar to your pup or dog. A look at the highlighted dogs will give you a good indication of which dogs contributed the most genetic influence to your pup or dog’s running style. The more your highlighted dogs trace back to the doubled up dogs, the greater the degree of inbreeding on them.

So, in determining the degree of inbreeding, don’t just look for the number of individual dogs in a pedigree or the number of times dogs were doubled up. In addition, use the above methods to determine to an even better degree the influence certain ancestors had on your pup or dog.