Re: [PyrNet-L] SAS. threat to Pyrs??

[Kshoffman@aol.com]

In a message dated 12/21/99 1:45:50 PM Eastern Standard Time, 
JGentzel@aol.com writes:

Quoting me:
>>>
  The most current knowledge and understanding of genetics and heredity 
  indicate that linebreeding likely conceals (for generations) just as many 
  things from a breeder as outcrossing might disguise. With complex modes of 
  inheritance, you may not *know* something is there even with linebreeding 
or 
  inbreeding on a very small gene pool you are intimately familiar with, 
until 
  it is too late.
>>>
 
<<Can you reference this knowledge?>>

Keep in mind, this paragraph was in context with the rest of the post.  That 
is, with complex polygenic modes of inheritance such as threshold type 
defects, and impairment of fitness traits that results from an accumulation 
of suboptimal alleles over time, linebreeding can hide for generations what 
is going on genetically.  This is because like pairs of involved deleterious 
or suboptimal alleles are gradually being accumulated over each generation, 
until it reaches the point where the level of impairment becomes obvious and 
"visible" to the breeder.  A breeder may have no indication that this is 
happening *until* fitness is noticeably impaired, or until the threshold is 
crossed that results in expression of a polygenic defect.

These statements are not based on one or two references, but on a vast amount 
of written material I've collected and studied over the past two years based 
on recent research in genetics and related fields.  This has involved 
literally hundreds of hours of research on my own personal time, as well as 
over a year of participating on the Canine Genetics Discussion list, and as a 
result of that forum, having the opportunity to consult with numerous 
professionals in the field.

As regards references, I think the URL I provided on the inheritance of 
epilepsy in Belgian Tervuren is one excellent example. (Did anyone take the 
time to read it?) Of course, others don't likely have the benefit of studying 
the history and foundation of the breed that I do, but I can assure you that 
in the beginning, both inbreeding and tight linebreeding were used quite 
heavily in an effort to establish and fix type and optimally desired 
"coloration". This went on for decades, and few if any breeders realized at 
that time that what they were doing was slowly accumulating and fixing all of 
the genetic variables that eventually resulted in the expression of epilepsy. 
We are now paying the price for this as evidenced by our rate of epilepsy in 
the breed, which can anecdotally be traced back to just a few dogs that 
everyone bred to, forsaking all others, one of whom can easily be classified 
as the "father of the breed."  It is virtually impossible to find a line 
worldwide that did not initially heavily inbreed or linebreed on these dogs.  
I can't imagine breeders would have done that if they new what consequences 
we would be facing today as a result of that practice.

How about Dalmatians?  Decades of emphasis on linebreeding and inbreeding to 
fix the optimal, perfect coloration and pattern eventually resulted in the 
loss of the allele for normal urinary function.  It is generally assumed both 
by breed fanciers and by scientific researchers that not one single AKC 
registered Dalmatian carries the allele for normal urinary function.  Every 
Dalmatian has the genetic makeup to express a urinary stone forming problem 
to varying degrees. Now, the breed is facing a rate of 10-12% bilateral 
deafness, and an additional 20+% unilateral deafness as a result of this 
practice as well.  Research on the problems the Dalmatian breed faces 
indicate crucial alleles coding for a necessary enzyme in urinary function, 
and crucial alleles necessary for normal hearing have been or are being 
"tossed away" breed-wide as a result of decades of inbreeding/linebreeding 
with a selection emphasis for the "perfect" spotted pattern, as these mutant 
alleles in the breed lie closely linked on the same chromosome as those that 
produce the most optimally desired color/pattern.  I would certainly like to 
think this happened inadvertently over the decades, and NOT that breeders 
knew this was going on and just decided they would pay the price with urinary 
stone-forming deaf dogs in the name of *perfect* spotting pattern.  
(Mismarked dogs, those with larger than desired "patches" of black on the 
ears or about the head have a much higher rate of normal, bilateral hearing, 
but these are either severely faulted or disqualified by the standard.)

I would also recommend reading some of the excellent article links on the 
Canine Diversity Page, some written by serious breeders, some written by 
geneticists, mathematicians, statisticians, physicians, most of whom also 
happen to be fanciers or hobby breeders and prominent figures in their 
respective breeds, specifically as regards health research:

The Canine Diversity Page
<A HREF="http://www.magma.ca/~kaitlin/diverse.html">http://www.magma.ca/~kaitl
in/diverse.html</A>

There is a lot of material here to read, so if you don't want to take the 
time to browse through all the links on the Canine Diversity Page, here are 
some particular articles of interest:

"The Downside of Inbreeding: It's Time for a New Approach"
by C.A. Sharp
<A HREF="http://www.magma.ca/~kaitlin/price.html">http://www.magma.ca/~kaitlin
/price.html</A>

"The Price of Popularity: Popular Sires and Population Genetics"
by C.A. Sharp
<A HREF="http://www.magma.ca/~kaitlin/popsire.html">http://www.magma.ca/~kaitl
in/popsire.html</A>

"Diversity and the Purebred Dog: The Poodle and the Chocolate Cake"
by Dr. John Armstrong
<A HREF="http://www.magma.ca/~kaitlin/cake.html">http://www.magma.ca/~kaitlin/
cake.html</A>

"Eliminating Mutation: The Impossible Dream"
by Dr. John Armstrong
<A HREF="http://www.magma.ca/~kaitlin/mutation.html">http://www.magma.ca/~kait
lin/mutation.html</A>

"Genetic Diversity - the Dark Side of Inbreeding"
by Dr. Catherine Marley
<A HREF="http://www.lhasa-apso.org/health/divrsity.htm">http://www.lhasa-apso.
org/health/divrsity.htm</A>

"Inbreeding and Diversity"
by Dr. John Armstrong
<A HREF="http://www.magma.ca/~kaitlin/inbreed.html">http://www.magma.ca/~kaitl
in/inbreed.html</A>

"Inbreeding and Linebreeding"
by Dr. Sue Ann Bowling
<A HREF="http://bowlingsite.mcf.com/Genetics/Inbreeding.html">http://bowlingsi
te.mcf.com/Genetics/Inbreeding.html</A>

"Population Genetics"
by Dr. Sue Ann Bowling
<A HREF="http://bowlingsite.mcf.com/Genetics/PopGenI.html">http://bowlingsite.
mcf.com/Genetics/PopGenI.html</A>

"Phenotypic vs. Genotypic Heterogeneity"
By Dr. Leos Kral
<A HREF="http://aussie-health.westga.edu/research/general/hetero.html">http://
aussie-health.westga.edu/research/general/hetero.html</A>

"Multiple Gene Traits"
By Dr. Leos Kral
<A HREF="http://aussie-health.westga.edu/research/general/multigenic.html">htt
p://aussie-health.westga.edu/research/general/multigenic.html</A>

"Penetrance and Expressivity"
By Dr. Leos Kral
<A HREF="http://aussie-health.westga.edu/research/general/pen-express.html">ht
tp://aussie-health.westga.edu/research/general/pen-express.html</A>

"Breeding - Dogs or Pedigrees?"
by Dr. Catherine Marley
<A HREF="http://www.magma.ca/~kaitlin/assort2.html">http://www.magma.ca/~kaitl
in/assort2.html</A>

"Inbreeding in Dalmatians"
by Dr. James Seltzer
<A HREF="http://users.nbn.net/~jseltzer/coi_pub.pdf">http://users.nbn.net/~jse
ltzer/coi_pub.pdf</A>

"Congenital Deafness and Its Recognition"
by Dr. George M. Strain
<A HREF="http://www.lsu.edu/guests/senate/public_html/VetClinNA.htm">http://ww
w.lsu.edu/guests/senate/public_html/VetClinNA.htm</A>

I have plenty more, including scientific journal references, if anyone is 
interested.
 
I wrote: 
>>>
*New* and *current* scientific and genetic knowledge indicates that quite 
probably a vast number of genetic conditions that afflict purebreds ARE NOT 
simple autosomal recessives,
>>>
 
Joe responded: 
<< Would be surprised it this was "new".  It has always been this way hasn't 
it. 
  If anyone ever thought every trait was one gene they are very wrong.  We 
are 
 actually lucky when this is the case.>>

Unfortunately, Joe, I think a number of breeders are mistakenly under the 
impression that genetics is much simpler than it actually is.  However, like 
you, I have always suspected the "simple" modes of inheritance are few and 
far between. What's new is the advancements in molecular genetics that are 
allowing scientific researchers to *prove* this is the case.  Additionally, 
some projects to identify markers and genes related to modes of inheritance 
that were initially believed to be simple autosomal recessive based on 
pedigree analyses, are in fact yielding some surprises. For example, 
Idiopathic Epilepsy in Belgian Tervuren was initially believed to be a simple 
autosomal recessive, as was von Willebrand's Disease in Doberman Pinschers, 
but in the process of developing a DNA test for the latter, it was determined 
the mode of inheritance, while autosomal recessive, is a bit more complex and 
involves variable penetrance and expression.

<A HREF="http://www.vetgen.com/vwdrpt.html">DNA Studies in Doberman von 
Willebrand’s Disease</A> 
http://www.vetgen.com/vwdrpt.html

Kelley Hoffman
kshoffman@aol.com