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Normal Parent + Normal Parent |
4 Normal Offspring |
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Normal Parent + Carrier Parent |
2 Normal, 2 Carrier Offspring
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Normal Parent + Affected Parent |
4 Carrier Offspring |
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Carrier Parent + Carrier Parent |
1 Normal, 2 Carrier, 1 Affected Offspring |
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Carrier Parent + Affected Parent |
2
Carrier, 2 Affected Offspring |
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Affected Parent + Affected Parent |
4
Affected Offspring |
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Step #1
No dog with unknown genotype will be bred. ALL
dogs must be DNA tested for this to work! |
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Step #2
An affected dog is bred with a DNA-tested Normal dog. All puppies
will be carriers, but none will be affected. |
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Step #3
The carrier pups are bred to another DNA-tested Normal dog. Half the
litter will be Normal, half will be Carriers. All pups must be DNA
tested to determine which is which, as they do not come with labels,
unfortunately... The carrier pups can be placed as pets, or if they
are spectacular, Step 3 may be repeated, but it will slow down the
process. |
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Step #4
The Normal pups are then bred to another DNA-tested Normal dog. All
pups will be Normal! Voila! If the dog you start with is a carrier
rather than an affected, you can omit Step #2. |
About the
Author
Diane Klumb is
Co-Captain of the H.E.A.R.T.
team, and has been a breeder of sporting dogs (primarily Gordon Setters) since
1969. She and her husband Bill have produced dozens of bench champions, field
titles and top producers under the kennel prefix
Bydand over the last thirty years while operating a Hunting Lodge
and gundog training kennel.
Diane has primarily been
involved over the last year with collecting the pedigrees and CERF data
that were needed by Dr. Gelatt to determine mode of inheritance for
cataracts in this breed. According to her, anyone who still does not
believe that this is an autosomal recessive gene needs to take it up
with Dr. Gelatt, as his Curriculum Vitae speaks for itself.
Diane is a professional dog
artist, presents seminars on canine anatomy, and is a monthly columnist
for ShowSight Magazine. She is currently serving time as Recording
Secretary for the Havanese Club of America and is AKC Judges' Education
Coordinator for the breed.
Heart Breeders Open Registry
This is what one dedicated
club can do for its breed. Others have tried to accomplish the
seemingly impossible task of open, i.e. shared, genetic information.
They have failed due to lack of breeder participation. Many clubs
throw money at "health testing" and research but members fail to test
their dogs for fear of the results. The Havanese people have shown
that it doesn't have to be that way. If everyone shares,
and if breeders quit throwing stones at each other, and if the
scientific community revises its often accusatory stance on breeding
from carriers or even from affected dogs, H.E.A.R.T proves it can
be done. Real progress at a time when many breeds are facing total
ruination, possibly even extinction as a distinct breed is within the
grasp of those who care enough to take the first step.
Diane leads the way with the firm conviction that this is the "most
exciting time to be in dogs." From her point of view and with the
logic of science to affirm it, we agree. We therefore support
Heart Breeders and hope you will take time to study this article and
visit their website.
Your club can do it too. Study the model!
Handy
Links
to Related Genetics
Articles:
Helping or Hurting Purebreds?
Breeding brains and "dog" out of the dog?
Medical & Genetic Conditions
Penetrance, thyroid, hip dysplasia (Akitas)
Evolution Of Shar Pei
In-depth study direct from China
Primary Lens Luxation List
U.K. open listing study (MBT)
Lens Luxation In The Dog
A Breeder looks at the problem
Thyroid
Problems In The Akita
Genetic considerations & numbers
Genetic Problems
Easily corrected in ANY
breed
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Pentimento
A Brave New World
Diane Klumb / ©
TheDogPlace October 2000 -
I'm a self-confessed cover-to-cover Gazette reader,
always have been. Next to ShowSight (Joe made me say this!) it's my favorite dog
publication. It's funny, but everybody reads the Gazette in different order,
I've found. Most people start with their breed column. Me, I start with the
Secretary's Pages. Always. I find out the most fascinating stuff that way… Which
is how I originally found out about the MULTIPLE SIRES thing.
For those of you who don't
traditionally start with the Secretary's Pages, this is a pretty controversial
topic. It involves the registering of puppies from a litter with multiple sires,
based on DNA-testing of the offspring. Lord knows it happens, even to good
breeders occasionally, and sloppy breeders a lot.
Assuming you were aware of it -
That's like when the guy hollers “Oh, hell, Marge, Rufus jumped the fence again-
he's in with Blossom! No! no, Rufus… off! Down! Off!… Damn!” while he's tearing
out the door in his BVDs - under the old system, you either placed the resulting
litter in pet homes without papers or put down the sire whose name looked best
on the pedigree, depending upon your own personal Code of Ethics. (Now, with the
advent of DNA testing, Option Number Two is, to say the least, ill-advised.)
Unfortunately, most of the
controversy surrounding the issue seems to be based on that scenario at best,
and the validation of truly sleazy pack-breeding at worst. I say: who cares
about any of that? Fine the accident victims to make them more careful, keep
after the real scum of dogdom as best we can, whatever.. but quit missing the
point! Registration of multiple-sired litters is an incredible tool, and has the
potential to do more good for the canine world than anything else heretofore
dreamt.
You have no idea what I'm talking
about, right? That's OK, happens to me all the time ...
follow along: I have spent the last
year doing the pedigree research in a single breed for an autosomal recessive
disease as part of a CHF study, the ultimate goal of which is to isolate the
gene for hereditary cataracts, This involves locating dogs from three groups-
Normals (dogs not carrying the gene at all), Carriers (dogs carrying a single
copy of the gene, phenotypically normal, but passing the gene to half their
offspring) and Affecteds (these dogs have received two copies of the recessive
gene, and are very likely to develop the disease, although, for unknown reasons,
they may not). DNA from those three groups are then compared in order to isolate
the gene. (For the scientifically-challenged, the principle is a bit like the
old Sesame Street song... “One of These Things Is Not Like the Other”…for the
other three of you, it includes homozygosity mapping and linkage analysis study
..)
Now, the only problem is, we've had a
hard time coming up with any Normals. In a year of scouring the country, and
testing the offspring of any likely candidates, we've come up with two. One is a
neutered twelve-year-old male, and the other was a thirteen-year-old bitch, who
unfortunately has since died. What this indicates is a gene pool that is pretty
thoroughly contaminated. And this breed is not alone!
What appears to be happening is that
by the time the causative gene or gene marker for a disease is discovered, it's
also discovered that it's pretty well spread throughout the population. The
chart on the next page shows clearly how that happens. It is virtually
impossible to eradicate a recessive gene from a population without a DNA test.
It will only get progressively worse. If the disease is late onset, as many are,
it is even harder (harder than virtually impossible?) because affected animals
are unwittingly bred, and pass the gene to all their offspring. Copper
toxicosis, Von Willebrand's, and PRA are all examples of diseases that have
frighteningly high incidence rates in their respective breeds. Once the gene for
hereditary cataracts is isolated, it is likely to be the same story. The reason
for the high rates of contamination is the same reason we have quality dogs- we
linebreed. So be it. That's not an indictment of the practice, it's just a fact.
And we tend to linebreed off the same quality animals. If one of them is
carrying a recessive gene, it's gonna get around...
What most breeders don't realize is
this: With an autosomal recessive disease, for each affected dog in a pedigree,
every one of his offspring, both his parents, half his siblings, at least half
his parents' siblings, at least two of his four grandparents and at least half
their siblings are carrying the gene. That's a lot of carriers. So if you have
an incidence rate of, say 25%, you'll be lucky if 25% of the of the breed is
Normal. Yet people are always surprised....
OK, here's the good news: Once you
have a DNA test, be it a linkage-analysis (gene-marker) test or a direct test,
the disease can be completely wiped out of that breed in three generations
without ever removing a single dog from the gene pool or producing a single
affected dog ever again.
This is a critical fact to
understand, because it is that particular fear that has kept breeders from
co-operating in the past. Historically, only the most courageous of breeders
have stood up and said "My stud dog is affected," or "My stud dog is a carrier."
It is the single most devastating thing a breeder ever has to do, and many of us
are simply incapable of it. So we either don't look, or we don't tell.
Ethically, there is very little difference between the two. "I can't expect my
pet owners to test their dogs!" is a euphemism for "I don't want to know my dog
is a carrier because then I'll have to stop using him!" and there is no way
around that, kids.
But once that fear is removed, there
is no reason not to rid a gene pool of a recessive disease. If the disease is
not lethal or debilitating and doesn't affect his sperm count, there is NO – I
repeat: NO-reason that an affected dog cannot be bred. Now, geneticists will gag
a little over this, as they currently recommend breeding only a percentage of
carriers, and certainly not affecteds, yadayadayada, but they are not breeding
showdogs, either. Breeding off the affecteds will slow down the process by a
single generation, because all the offspring will be carriers, but it will also
allow breeding programs to continue without sacrificing years of work in the
areas of breed type and soundness and movement, which are fairly alien concepts
to molecular biologists. These guys do not understand the complex psychology
that keeps breeders from using an available DNA test that they spent years
developing. They are frankly baffled by the ridiculous excuses breeders are
coming up with, when they slaved long and hard over their electron microscopes
to come up with these tests. They think breeders are idiots...
I, on the other hand, understand
completely. Let's look at the English cocker. (I had Engies, by the way, for
fifteen years, and I have more than a passing personal familiarity with PRA, so
get off my back…) They've got a DNA test for PRA. I have heard every conceivable
excuse for why breeders are not using it. “It's just a gene marker. It's not
100% accurate.” SO? Although there is a possibility that a carrier may actually
be normal, or an affected dog may in reality only be a carrier, as long as a
normal is a normal, it doesn't matter! “We don't know if it really will work.”
Not until you try, that's for sure ... "Some dogs are turning up as affected,
but aren't going blind.” I'd say be happy for them-but it doesn't change their
genotype. Or my personal favorite: “Optigen is just making money off us
breeders.” Yeah, well, last time I looked, so were Iams and Pedigree and Purina,
but that's hardly a good reason to quit feeding your dogs ... who GIVES a damn?
NO, the real reason, although all the
nonparticipators will deny it, is in the results of the tests that have been
done. Only twenty percent of the English Cockers tested last year were Normal...
Which means if you have your dog DNA
tested, odds are good he won't be Normal, and there go your hopes, dreams, years
of work and reputation.
But that is bullshit, pure and
simple. That's applying 16th Century morality (stoning, witch-hunting and the
like) to 21st Century molecular biology. If we want to achieve perfection in
purebred dogs, which is the holy grail of dog breeding, we have to stop being
stupid. New Rules apply, and we, as ethical breeders, must write them as we go.
No one can write them for us, because no one else understands what we are about.
Study the two charts carefully. They
are instructions for permanently removing a recessive disease gene from any
population of dogs without removing a single dog from a breeding program. And no
affected animals will be produced in the process, which is important. Nothing
need be sacrificed-not type, nor soundness, nothing.
Now, there is one problem with this
program. Let's assume that 20% of your breed tests Normal. Those dogs become
"universal donors" and are largely responsible for eradicating the gene. Now,
Nature being what it is, half of those animals will likely be bitches and half
will be males. And the odds are good they will not be young animals, either, if
you're looking at those percentages, because as the gene pool becomes more
contaminated with each generation, the number of Normals decreases.
Logic tells us Normal males, even
older ones, comprising 10% of the population, can easily service 40% of the
total population, which would be your carrier and affected bitches. Geography is
not a huge problem, either, because of the avail- ability of chilled and frozen
semen.
But where does that leave the carrier
and affected males? These males would also make up 40% of the population, but
can only be safety bred to 10% of the population, and these will likely be
bitches approaching or past middle age, with a limited number of litters left in
them. This problem is going to create a genetic bottleneck, and those
bottlenecks are generally what got breeds into this mess in the first place ...
it is imperative that these dogs make a genetic contribution for the overall
health of the population, because when a gene pool is bottlenecked, the
possibility of introducing a gene more deadly than the one you are trying to get
rid of often rears its ugly head. But there aren't enough Normal bitches to go
around.
OK, guys, have the lights gone on
yet? Did the term Multiple Sires just pop into your head?
As more DNA tests become available in
more and more breeds (and they will) and as breeders learn how to use them to
eradicate genetic disorders, the concept of Multiple Sires will come to be a
viable, everyday tool in creating a healthy gene pool. A single Normal bitch
could be artificially inseminated with the semen from four quality males,
thereby quadrupling her genetic contribution, as well as maintaining the
contribution of those four males, three of whom would otherwise be excluded from
the gene pool for lack of a "safe" mate, without forcing her to have four
litters.
This is 21st Century dog-breeding,
guys. Finally, with the tools available to us, we truly won't have to throw out
the baby with the bathwater ever again.
Now, if in order to do this we have
to put into place a program that will let sloppy breeders register a litter out
of two sires because 0l' Rufus jumped the fence again, so be it. I've got a News
Flash for you-he was gonna register that damn litter anyhow. He's been doing it
for years ... at least this way the integrity of the Studbook is maintained.
Slap him with a big fine and he'll just go back to his old method, because it
was cheaper, and he's unlikely to get caught anyway.
We cannot
expect the AKC to legislate stupidity, sloth or greed out of this sport, much as
we may badger them to do so. But we can expect them to lead in the quest for
better, healthier dogs. And this is a big step forward. If you are a breeder,
and all this was news to you, go buy Future Dog, Breeding for Genetic Soundness,
by Patricia J Wilkie. It's available from CHF. Old Breeders can learn new
tricks, and if you're not part of the solution, my dears, you know the rest of
the line....
~ Diane
Klumb
reprint permission
SHOWSIGHT MAGAZINE/OCTOBER 2000
http://www.thedogplace.org/Genetics/BraveNewWorld-00101005_Klumb.asp
Related
Genetics:
http://www.thedogplace.org/Genetics/Painting-Genes-06021005_Andrews.asp
http://www.thedogplace.org/Genetics/Genetic-Problems-0110_Hays.asp
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