[pyrnet] Consider breeding carriers (a proposal)

["Linda Weisser" <lmweisser@olywa.net>]

From: Impyrial@aol.com <Impyrial@aol.com>

>I am not sure that it has actually been "proven" that it is in fact a
simple recessive.  It was assumed by the newfoundland people that dwarfism
was a simple recessive and a test breeding of two dwarfs was done.  Two
puppies of six lived and both were normal! >>

I suppose that "proof" would rest on breeding two dwarfs and seeing if we
get an all dwarf litter and then that result would have to be repeatable.
Statistics being what they are.  Anyone who has or knows of two intact,
opposite sex dwarfs and would be willing to let them produce what may be a
100% dwarf litter, I would appreciate their contacting the health committee
and let's talk about it.

So, why do we assume that it is a recessive?  Firstly, of course, the fact
that in almost all particulars it seems the same as Mal chondroplasia and
we know that that is a simple recessive.  Secondly the health committee
collected in excess of 20 pedigrees of dwarf litters that included total
numbers and dwarf numbers.  These pedigree and numbers were sent to Dr
Padgett for his analysis.  Recessives are identified by their
characteristic "fingerprints" of numbers of affecteds to total numbers
based on litters across the board, not on a single litter.  When we add all
of the known "dwarf" litters the numbers are "classic"--25% affected.  The
fingerprint of a recessive.  Now this may be a somewhat blunt instrument
but it is the one most used.  Again, if anyone wants to volunteer for a
dwarf to dwarf litter (preferably more that one out of unrelated dogs)
please come to us and talk.

I do think that it is *extremely* important to remember that what occurs in
Newfs and is sometimes called "dwarfism" is almost certainly *not*
chondroplasia such as is found in Pyrs and in Mals.  Indeed what is
occuring in Newfs is usually called something like "elbow anomaly" or some
such.  It does not result in the kind of short statured, "balanced" dwarfs
that we see in Pyrs.  Newf "dwarfs" have exceptionally short front legs and
more or less "normal" hind legs.  This is simply never seen in dwarf Pyrs
although something approaching that is seen in some Mals.  There are many,
many different kinds of dwarfism and we need to be very careful not to lump
them together.  And the mode of inheritance of these different
manefestations, varies.  Dr Sande at WA state U, Pullman who may well be
the dwarf expert in the world, thinks that what we see in Pyrs is
essentially what they see in Mals.

There are no "easy" outs and actually we are much better off if this is a
simple recessive than if it is not.  We can count ourselves fortunate.

Linda Weisser
GPCA Health Committee co-chair (for those who don't know me )
lmweisser@olywa.net