<%@LANGUAGE="VBSCRIPT" CODEPAGE="1252"%> DNA Information - Camerata Reg'd Kennel
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Highlights:

· About Bedlingtons

· DNA Information

· Bedlingtons of England
  Rathsrigg Bedlingtons
  Hilldyke Bedlingtons

 

     I decided to set up this page in an effort to share with you my understanding of what the current DNA test for Copper Toxicosis (CT) is all about, and what it means.

     Early in 1996 we and many other breeders around the world began submitting samples to various laboratories for DNA testing for CT in Bedlingtons.

     Since then, there has been much confusion in that many times the DNA results were not supported by the liver biopsy results which have always been the more definitive test. Now, the various laboratories have changed protocols, and will not venture so far as to even call a dog affected, carrier or non-carrier. What breeders get now are merely numbers representing the alleles found using the microsatellite marker C04107.

     It is important to remember at this point that the actual gene has not been identified. This is merely a linkage test, the value of which depends on the breeder finding a link in their pedigrees to an affected dog.

Chart of inheritance:

Sire Dam Puppies
1-1 1-1 All 1-1
1-1 1-2 1-1 and 1-2
1-1 2-2 All 1-2
1-2 1-1 1-1 and 1-2
1-2 1-2 1-1, 1-2 and 2-2
1-2 2-2 1-2 and 2-2
2-2 1-1 All 1-2
2-2 1-2 1-2 and 2-2
2-2 2-2 All 2-2

     The above illustrates what should happen in breedings when the allele numbers of the parents are known. To make any sense of these numbers, the breeder must find out what the 1's and 2's mean in his or her individual bloodline. It is not correct to automatically assume that a 1-1 dog is a non-carrier (commonly called clear) and a 2-2 dog is affected. There have been enough cases of the opposite to prove this.

     Following are some examples of how to find the link in a pedigree (these are actual cases).

Case 1:
Puppy in question has a DNA result of 1-1
Sire: DNA 1-2 and was biopsied unaffected
Dam: DNA 1-2 and was biopsied unaffected

At one year of age, the puppy was biopsied and found to be affected. Therefore we can assume that the "1" from both the sire and the dam are the so-called "bad" genes. Because both the sire and dam had biopsied normal, that meant their "2" had to be good. Therefore, any puppy that was DNA 1-2 from this breeding would be a carrier (bad "1" and good "2") and any puppy that would DNA 2-2 would be clear (non-carrier) as both 2's would be good.

Case 2:
Puppy in question has a DNA result of 2-2
Sire: DNA 2-2 and was biopsied unaffected
Dam: DNA 2-2 and was biopsied unaffected

At one year of age the entire litter of five puppies (all DNA 2-2) were biopsied unaffected except for one puppy. Since there was an affected puppy, we know that both parents are carriers, yet we cannot tell which is the bad and which is the good gene. They are both identified as "2". We should also note here that two carriers bred together can produce affected, carrier and non-carrier puppies! That means that of the four unaffected puppies in this litter, some may be carriers and some may be non-carriers (clear).

     To illustrate further, let's suppose you bred the two puppies from the above cases together, (this is only hypothetical):

Parent 1: DNA 1-1 biopsied affected
Parent 2: DNA 2-2 biopsied unaffected

Offspring: All puppies will have a DNA result of 1-2. We already know from our above cases that the "1" would be bad as that parent biopsied affected. We also know that either one or both "2"s from Parent 2 are good since that dog biopsied unaffected. For the resulting puppies then, the unfortunate ones that inherited the bad "2" will be affected and the fortunate ones that inherit the good "2" will be unaffected, but carriers.

In either case all the puppies will have the same DNA result ... that being 1-2. The only way to tell then if any are affected is through the liver biopsy.

     In many bloodlines and in many countries, breeders have managed to find links in pedigrees and what has been found is that, usually, the allele number "1" is linked to the "good" gene and the "2" is linked to the "bad" gene.

     We wish to stress however, that this is not always the case. Every bloodline can be different. It is no good to assume that a 1-1 dog is a non-carrier or a 1-2 dog is a carrier or a 2-2 dog is affected simply because of the numbers. A link must be found in the pedigree in order for it all to make any sense.

     To further the point. There is an actual stud dog that has a DNA result of 1-2 and was test bred and proven to be a non-carrier (clear). That means he is producing offspring with good "1"s AND "2"s.

     One last point ... please remember, that according to the laboratories, even if a link can be found in your pedigrees, it is only 95% certain. They still recommend that breeders continue to liver biopsy all dogs.

     This is only our understanding of the current DNA testing protocol for CT in Bedlingtons. We still continue to use the DNA test as we believe it has some value, yet we also continue to have a biopsy performed on all our dogs as we also believe in being safe. The results from both tests used in tandem can many times give encouraging results.

     Please take this information in the spirit it is being provided. This is not meant to accuse anyone of anything, merely to provide what we hope is useful information.
 

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