[ SHOWGSD-L ] Re: showgsd-l Digest V6 #10
- From: RopajaGSD@xxxxxxx
- To: showgsd-l@xxxxxxxxxxxxx
- Date: Mon, 2 Jan 2012 20:05:57 -0500 (EST)
Jessica, This article although a bit lone...may be of interest to you and
others...
Please note this article was published in the February issue of
ShowSight Magazine and was written by Diane Klumb.
----------------------------------------------------------
The Mystery of the "Bad Bite"
Elementary, My Dear Watson
by Diane Klumb
Anyone who knows me at all probably also knows how totally excited I am by
the ability of molecular genetics to solve the mysteries inherent in the
breeding of purebred dogs. In addition to allowing us to actually "breed for
improvement" instead of just blithely throwing the term
around, I firmly believe that if used wisely, this new store of knowledge
represents our best hope for both preserving the sport of dog breeding for
future generations, and for fending off our own personal Professor Moriarty
in the guise of Ingred Newkird & Co. But actually using this new knowledge
to our benefit, and to the benefit of dogs, often requires us to discard
long-held and long-cherished beliefs. Realizing that something we were
taught years ago (and in many cases have passed on to the next generation of
breeders) was based on an incorrect assumption, and may actually be flat-out
WRONG, can be a
difficult mental pill to swallow, and some people just can't seem to do it.
For others, it provides an "Ah-HA!" moment, when the seemingly
inexplicable suddenly becomes clear. One such moment for me occurred a few
years ago,
when I learned that prenatal disruption (via genetics or environment) of a
regulatory gene with the delightfully improbable name sonic hedgehog (SHH)
often results in asymmetry, where the two sides of a dog don't exactly
match. (It's a lot commoner than you'd expect, actually, and occurs in people
to varying degrees as well. And symmetry in people has been linked to both
beauty and longevity. Probably true in dogs as well.)
More to the point, an asymmetric dog will invariably crab, as he has
longer reach and more drive on one side than the other, causing his forward
progress to eerily resemble that of a '63 Ford Fairlane with a bent frame. Yet
stacked in profile the dog displays flawless balance, which has confounded
judges and breeders since time immemorial.
When I shared that discovery in a column a few years back, an amazing
number of judges who read it made a point of telling me that it was an "Ah-HA!
moment for them, too. (One told me that now whenever she sees a dog
crabbing, she checks the elbows on both sides, and one is invariably set
higher on
the ribcage than the other.) An old dog show mystery solved by molecular
genetics. Cool.
I had another of those "Ah-HA! moments recently, when I stumbled upon a
fascinating research paper while looking for something else entirely.
(Happens to me all the time.) It seems that scientists have discovered that
the
size and shape of the mammalian mandible (or lower jaw) is controlled by a
surprisingly large number of genes - over 15 have been identified to date. A
little more digging revealed that an equally large number are involved in
the development of the maxillary complex, or what we refer to as the upper
jaw. The kicker is......they are different genes, and inherited pretty much
independently. Which means, in terms expressed as simply as humanly
possible: A DOG CAN INHERIT HIS UPPER JAW FROM ONE PARENT, AND HIS LOWER JAW
FROM
THE OTHER.
Ah-HaH! Another dog-breeding mystery solved, and a long-cherished belief
laid to rest. Putting this into an everyday breeding scenario, here's what
too often happens. A young health-screened dog of quality with a magnificent
head is widely used by breeders on bitches who's heads could use some
improvement--depending on the breed standard, their muzzles could be a little
shorter, or a little longer, or maybe a little more or less refined. But
rather than the overall improvement in the first generation breeders are
hoping for, they get maybe one nice bite (if they're lucky and depending upon
what the bitch's parents looked like) and a basketful of "bad" bites. (What
constitutes a bad bite varies from breed to breed, of course.) Soon the word
goes round that this lovely-headed dog "throws bad bites" and his stock
drops faster than Lehman Brothers. Happens all the time.
And now we learn that it wasn't his fault at all, poor guy. Breeders have
been laboring for years under the misconception that an off-bite is the
result of an AR gene, and that some dogs are carrying a recessive gene that
causes them to "throw bad bites." I've heard it said a thousand times over
the years, and so have you. But it is simply NOT TRUE. Turns out there is no
single AR gene for an undershot bite, or an overshot bite, either. There are
literally dozens of genes involved, all inherited more or less
independently. So, from this day forward (unless you are one of those people
now
recognized as incapable of changing a long-held opinion in the face of new
evidence due to insufficient activity in the anterior singulate cortex and I'm
wasting my time here) we can all stop blaming the poor stud dog.
What is actually happening genetically is this: Given Mendel's Law of
Independent Assortment, which is still scientifically valid after all these
years, a percentage of the pups from an "unlike-to-unlike" breeding in the
head department will inherit a larger percentage of the genes for a longer
mandibular (under) jaw from one parent, and a larger percentage of the genes
for a shorter upper maxillary (upper) jaw from the other, resulting in bites
that are undesirable per a particular breed's standard. NEITHER parent is
to blame - malocclusions of the jaw, we now know, are polygenic.
Now, hopefully most of us already understand that there is a huge genetic
difference between a MALOCCLUSION OF THE JAW and MISALIGNMENT OF INCISORS,
which cause a reverse scissors bite in a dog whose jaws align according to
the standard, and whose "puppy bite" is often perfect. Misalignment of
incisors is usually caused by no more than the particular timing of the
eruption of the individual permanent teeth - if it is off, the upper incisors
will
force the lower ones out, resulting in a reverse scissors. (That's why
it's correctable with mere pressure.) There's no sense blaming this one on
either parent, either: Research has shown there are more than FIFTY different
genes that influence the development, and timing of eruption, of teeth.
Some of these genes, it turns out, are involved in other processes and also
code for traits that we've actually selected FOR over the years---the MITF
gene, for example, which is involved in pigment development (parti-colored
dogs are parti-colored because they carry a mutation on this gene) is also
involved in tooth development and timing of eruption, which is likely why the
parti-colored pups in a litter often get their teeth later than their
solid-colored brethren. The RSPO2 gene is also involved in tooth development,
and a mutation on this one is responsible for canine head furnishings. (And
that's just two off the top of my head, no doubt there are dozens more, as
we now know that genes "multi-task.)
Pauline Moon - _www.ropajagsd.com_ (http://www.ropajagsd.com/)
Ropaja German Shepherds:Member-GSDCAmercia & GSDCAtlanta - Best In Show
AKC JAM/AOE/ BISS CH Ropaja's Chateau Beaujolais OFA HIC; BISS AKC CH
Ropaja's Chateau Beaulieu OFA HIC; Multi BOB & GRP W AKC CH. Ropaja's Je Suis
Fleur De Lis; Multi-BOB & GRP W AKC CH Ropaja's Je Suis Gabrielle.
In a message dated 1/2/2012 7:53:17 P.M. Eastern Standard Time,
Showgsd-l@xxxxxxxxxxxxx writes:
Date: Mon, 2 Jan 2012 18:19:02 -0600
Hi All -
I already posted to the Dal list, but am curious to see what people here
also think. I have a Dal pup (sorry, not a GSD pup - yet), from the litter I
did last summer. She is 5 months old and has shed most of the major teeth
including her canines. When she was about 3 months old, I noticed she had
a base narrow puppy tooth, but let it go, knowing she was going to shed it
out shortly
She has now shed it out, but I noticed the lower adult canine is still not
perfect, but when I open her mouth, it does tip outward and the alignment
from the front is fine and of course, she doesn't have her adult molars and
premolars in yet, so hard to tell on the sides.
What is your opinion or how have you dealt with this? Should I be doing
something or should I just ride it out for awhile. I have seen bites change a
lot through the years, but have never had any dealings with this. Her sire
and dam have PERFECT mouths with complete dentition and there are mostly
beautiful mouths in her pedigree. She has a head shape different then
everyone else in her litter and I am hoping that when she grows some under
just,
it will take care of the tooth issue.
Any other suggestions? She's not in pain, eating with no problems and
overall perfectly healthy. I don't plan to breed her, but would like to show
her, but that isn't at the top of my priorities either..
Feel free to email privately - I am just looking for information.
Jessica MacMillan
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