Badger Lair is the underground home of Glen of Imaal Terrier enthusiasts.

Friday, February 24, 2006

AUTOSOMAL RECESSIVE

The following piece is about the genetic disease PRA found in Glen of Imaal Terriers.


Autosomal Recessive


This chart shows the expected results of particular matings, based on the genotype and phenotype of the parents. Before you study it, however, be aware that, to date, we have managed to find no Normal dogs. We will continue to test offspring. We will not be able to identify Normal dogs until we have a genetic marker linked to the DNA sequence of PRA.















































































NOTES:
The results of the above matings are on average. This is the chance for each pup individually. For example each pup produced in a mating between two Carriers has a 25% chance of being a Normal, a 50% chance at being a Carrier, and finally a 25% chance at being an Affected.
Orange dogs and yellow dogs are genetically identical. Both appear Normal, but carry a copy of the defective gene, which they will pass to half of their offspring. The difference is in origin.

Orange dogs have an Affected parent which means that we know their status after the parent is diagnosed as Affected. They have to be at least a Carrier because their Affected parent passed the gene to all its pups.
Yellow dogs are those who have produced offspring with PRA. Same genetic phenotype and genotype, but we don't find out until they produce an Affected.
Blue dogs are not really identifiable. We do not know which dogs are truly Normal.
Red dogs are identifiable, after the fact. We know a dog is Affected once it is diagnosed with PRA.

________________________________________


Every dog has 39 pairs of chromosomes. Each chromosome contains thousands of genes. A dog receives one of each chromosome pair from each parent. Thus it has TWO copies of each gene, one inherited from each parent.

Over the course of time, the DNA sequence of a gene may undergo mutation, forming a new sequence or allele, . A new allele may cause a change in the biochemical action of the gene. A dog may inherit the original allele, or it may inherit one of the new alleles, but it will receive one allele from each parent.

In dogs, most of the mutations that cause disease are recessive. For a recessive mutation to cause disease, a dog must receive two copies of it, one from each parent. If the dog receives one Normal allele, and one recessive mutation, it will appear Normal, but will pass the recessive allele to half his offspring on average. This dog is referred to as a heterozygous Normal, or a Carrier. He displays the dominant gene, but carries the recessive. Alternatively, if a dog inherits a Normal gene from each parent, he will be a homozygous Normal.

Without a DNA test, it is impossible to tell if a dog is carrying the recessive mutation unless:
1. One of the parents is Affected, or
2. It is bred to another dog also carrying a copy of the gene, and one or more of the resulting pups is Affected.
A recessive mutation can spread fairly rapidly through a population before breeders are aware of it, especially if the number of breeding individuals is small. Carriers, who will test Normal all their lives, will be bred and pass the gene to half their offspring on average. If the disease is late-onset, many Affected dogs will be bred unknowingly. An Affected dog, carrying two copies of the mutation, will pass the trait to 100% of its offspring. This spreads the gene even faster. The number of Carriers will rise exponentially with every generation.
At the time that the first Affected dog appears in a pedigree, many of the dogs in that pedigree will be Carriers. For each Affected dog identified, both his parents, at LEAST two of his grandparents, and all his offspring will be carrying the gene. Without a DNA test to identify the Carriers, it is virtually impossible to eradicate a recessive disease from a gene pool. The result is that Virtually all breeds have genetic problems.

Efforts to find the "cleanest" lines and to avoid "dangerous" pedigrees are a waste of time. Reducing a small gene pool by trying to avoid particular dogs in a pedigree will likely only result in the appearance of other, deadlier, recessive diseases and probably won't significantly reduce the risk of producing PRA. Removing the Carriers from the gene pool would be impossible- we'd have very few dogs left to breed except the young and untested ones!
Dogs that are past the age where they may develop PRA themselves, but are documented Carriers, are in fact among the "safest" dogs to breed at this point, as we have no actual Normals yet. These dogs will only pass the gene to half their offspring.

Very young dogs (under two) even if CERFed clear are probably the riskiest, as they may be undiagnosed Affecteds. An Affected dog will pass the gene to 100% of his offspring, which will result in more Affected pups being produced.

An older dog with clear parents, a good number of CERFed offspring and no documented Affecteds to date would be the safest, but these dogs are rare. They qualify as "possible" Normals.

Obviously, no breeder WANTS to produce dogs that will develop PRA. The best any breeder can do is to breed for type, soundness and temperament, perform CERFing annually, and share information on parents, siblings and offspring both with other breeders, so they may also make informed decisions, and with researchers, who will ultimately isolate the gene and develop a diagnostic DNA test. In order to more quickly develop such a diagnostic test, ALL dogs have to be DNA tested. Once a DNA marker is found, the following breeding rules should be followed:

1. No dogs with unknown genotype should be bred. This of course would be an ideal case. Realistically a dog with an unknown genotype should at the very least be only bred to a known Normal.

2. An Affected dog should be bred only to a DNA- tested Normal dog. All puppies will be Carriers, but none will be Affected.

3. The Carrier pups are bred to another DNA-tested Normal dog. Half the litter on average will be Carriers, half will be Normal. All pups must be DNA tested

The Normal pups are then bred to another DNA tested Normal dog. All pups will be Normal. If the dog you start with is a Carrier rather than an Affected, you can omit Step # 2.

If even 10% of the breed tests Normal, there should be enough to work with so that type, soundness and temperament won't be sacrificed. Carriers could be used for breeding until the population is in good shape, at which point the prudent thing to do would be to try and breed only the Normals. But all dogs would ideally be tested, and no one would breed from an untested dog to avoid re-contaminating the population
If all dogs are tested, there would never be another Affected Glen. In breeds where a DNA test for a recessive gene is available, the cost of testing is between $150 and $200. Is there anyone who wouldn't pay that to insure that their dog wasn't going to go blind?

Eliminating PRA is an achievable goal. To date, the gene for PRA has not yet been identified in Glens.
Finally, Ara Lynn in reviewing this manuscript cut right to the point with this succinct observation. Following quote used with Ara’s permission.

“All you need do to avoid creating blind dogs is to make sure that one of the mated pair is truly normal. After that, it is a moot point. As long as you are not creating blind dogs, it truly doesn't matter how long carriers remain in the population. In a theoretical world maybe it would be nice to eliminate the recessive gene, but in the real world you will never get total cooperation towards that goal. There are many many characteristics desirable in Glens. Perfect eye genetics should not be the overriding factor. And remember, even with genetic tests, you may still end up with false positives and false negatives.

We dog breeders and exhibiters are really into perfection and absolute control. There is no such thing on either count.”

Adapted and edited by Bill Amaral, from a web page that no longer seems to be up, with permission to use, from:
http://www.firestormkennel.com/homepage.html

Thursday, February 23, 2006

Gallery of a Few Glens

The Glen of Imaal Terrier should possess great strength and should always convey the impression of maximum substance for size of dog. Glens come in two colors wheaten and blue brindle.












All of these photos are copyrighted.

Tuesday, February 21, 2006

The Glen of Imaal

The Glen of Imaal Terrier comes from the Glen of Imaal in the Wicklow Mountains of Ireland. They were a best kept secret for many many years. Here are some photos of the area in Ireland and one even has a Glen of Imaal Terrier in it.



Monday, February 20, 2006

Energetic Glens and Agility

By Michelle Du Bois
under the watchful eye of Briarhill Amanda CD, MX, OAP, AXJ, OJP, AD, PII, JS-N, RS-F, GS-N, EAC, OJC, TN-O, TG-O, OGC, JS-N, RS-E, GS-N, CL3-S, RL1



When I got my first Glen, I discovered that she had a higher level of energy than I expected. I have since discovered that there seem to be two basic types of Glens – the high energy ones, and the couch potatoes. Granting that all Glens have both potentials within them, each one seems to have a natural proclivity toward one mode or the other.

The issue for me became what to do with that energy. I discovered the sport of dog agility. She was much too young to begin jumping around on her tender young joints, so I gave obedience a go. She hated it. Still, in all, she wanted to do what I asked of her and I give her a lot of respect for the effort. Eventually we found our way to Rally-O and fared a bit better. We also joined play groups and earned a Canine Good Citizen (CGC) title while we waited for her body to develop.

Since I am retired, she went everywhere with me and did everything that I did – the day after I brought her home, we delivered horses all over three states. She would get short potty breaks at each stop and then back in the truck for the next leg of the journey. Consequently, she has never had a problem behaving in a vehicle or in going new places. I think she truly believes that everything is just a new opportunity for her to meet people who will pet her and spoil her a bit. The time we spent in close proximity provided the opportunity for us to get to know each other pretty well. She never got a chance to misbehave and training was more a matter of letting her know what I thought she should or should not do rather than a correction for misbehavior.

So, finally, the time came for us to begin our agility training. I stumbled around, bought MANY books purporting to show me how to train my own dog to the agility sport. Some of them even showed me how to save money on equipment. Nowhere did I find anything that really understood that neither my dog nor I had the faintest clue what we were doing.

My Glen was not a food motivated dog, but tried the obstacles for the pleasure of hearing me get really excited when she got it right. Although she is a lot more motivated by food now, she still does better if people are cheering her on.

My Glen does not have a gentle mouth and tugging with her can cause major bruises on one’s hands. We have compromised on an occasional bruised hand in exchange for some quality, rather than quantity, tug play times as a reward.

My Glen is focused on an agility or obedience course and I attribute that to the time we spend together as companions. That relationship is probably the most important aspect of our agility successes. And those agility successes strengthen the bond in return.

I recommend to anyone with a Glen puppy who wants to dabble, or even compete, in agility, to:
• Go take a beginner course. The PC term around here is “foundation” course.
• Find someone who likes your dog and that you like.
• Find someone who understands that not all dogs benefit from the same training styles, reinforcements, rewards, and methods.
• Find someone who recognizes that not everyone wants the same thing out of the sport.
• Figure out what you want and find someone to help you decide if that goal is reasonable with your dog.
• Then have fun.

A couple of don’ts, although I mostly believe in dos:
• Don’t try and do everything by yourself, you will reinvent the wheel.
• Don’t feel that you have to spend lots of money over a long period of time on organized training. You just have to get the help to get started and then an occasional reinforcement when you need help with a new challenge.
• Don’t have a professional train your dog for you – you will miss the best parts.

Glens in Motion

The question is how should a Glen of Imaal Terrier move? The gait authority in the dog world, Rachel Page Elliott says in her book Dogsteps that "a strong, even gait is desirable in all breeds, no matter the size, the shape or the purpose." Correct movement is not something just show dogs need but is essential to performance, work, and play.

The start of any analysis of movement starts with the understanding of the unique structure of our breed and how it affects the movement our breed. The Glen of Imaal Terrier is a breed whose structure is due to achondroplasia, a "form of dwarfism primarily affecting the development of the long bones." (citing Harold R. Spira from Canine Terminology). The AKC standard of the Glen of Imaal Terrier (see link on sidebar) has many points that would make any judge of movement scratch their head and wonder how can a dog move with a gait that is rhythmic and effortless with these characteristics. A Glen is suppose to have a rising topline, bowed forequarters with turned out feet with a gait that is "free and even, covering the ground effortlessly with good reach in front and good drive behind. This is a working terrier, which must have the agility, freedom of movement and endurance to do the work for which it was developed." (AkC Glen standard). Yes, despite these features, Glens can move rhythmically and without effort and as one breeder says, "like a fine tuned locomotive." We want to see good drive in the rear and reach in the front. Many structural faults can give the appearance of either or both so one needs to analyze each structure to determine if a Glen is a sound mover. Some faults may be deceiving. For example, dogs who pitch or have a swinging of the rear legs or paddle in the front may look like it has good drive and reach. This piece on movement is just the tip of the iceberg and meant as a teaser for readers to focus on movement of our breed and for breeders to work to gain knowledge on structure and how it effects movement. There are great sources out there to study but nothing beats sitting ringside and watching not only Glens but also different breeds move. Remember that no dog is without its faults. Good breeders recognize these faults in order to eliminate them in future progeny. It should also be noted that many Glen exhibitors are not experienced dog handlers and may not be showing a dog well enough for anyone to really analyze the dog's movement.

Thursday, February 16, 2006

Movement in the Glen of Imaal Terriers

Seven Glen of Imaal Terriers were entered and shown at the 130th Westminster Kennel Club Show in NYC. For those not able to attend, the Westminster Kennel Club has provided video clips of each breed's judging. For the Glens, go to http://www.westminsterkennelclub.org/2006/video/breed/index.html

and then click on Glens to see the video. It takes a few minutes for the clip to download so be patient. You can freeze frames to see the movements better of each Glen. It is not perfect but is the next best thing to being there.

 
Web Site Counter
Online Universities