| PING Liisa and/or experts on merle and/or white factoring - CLICK HERE for the Pet Manual Forum Home Page |
| Sionnach |
A question for anyone knowlegable about merle: someone on one of the JRT
lists has posted pictures of a "new breed" that she and a few others have
created, allegedly by crossing JRTS (piebald gene, no merle in the breed)
Rat Terriers (also, AFAIK, piebald gene, very occasional merle in the
colored areas), and Patterdales (minimal or no white markings, no merle).
She showed four pictures of dogs. Of those dogs, one was solid black; all
of the others- including an entire litter of puppies- were merle with large
black patches (an effect similar to Catahoula markings).
She says she deliberately bred for a "different looking" breed, and that
the merle came from the Rat Terriers used. (Never mind the fact that it's a
breed DQ, and almost never seen.)
First question is, is the piebald gene dominant? If so, how would one go
about getting solid merles by breeding in a piebald merle dog?
Second thing- she appears to be claiming that the deafness/blindness seen
in homozygous merles is due to the white factor gene also being present,
and/or that the MM effect doesn't occur if you're breeding solid merles
(i.e. merles with no white markings). Is this the case?
It's not how I've understood anything I've ever read on the MM effect; I
don't recall seeing white factoring mentioned except in the context that a
heavily white factored Mm and a MM may LOOK similar (IOW, be primarily white
with small merle patches).
My understanding of the MM effect is that it can completely inhibit pigment
development- IOW, create white- in an area that would be diluted (merle) if
the dog were Mm, and fully colored in a mm dog.
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| Liisa Sarakontu |
"Sionnach" <rhyfelwr@msn.com> wrote in news:2jdr94Fvt6reU1@uni-berlin.de:
> First question is, is the piebald gene dominant?
Nope, but many (most?) Ssp dogs - one dominant solid gene, one piebald gene
- have minor white spotting like white paws and some white on chest. So,
piebald isn't fully recessive to solid but it certainly isn't dominant to
it. (But most piebald-type patterns in other species like cats, horses,
rabbits and gerbils are dominant to solid.)
> Second thing- she appears to be claiming that the deafness/blindness
> seen in homozygous merles is due to the white factor gene also being
> present, and/or that the MM effect doesn't occur if you're breeding
> solid merles (i.e. merles with no white markings). Is this the case?
Not totally true, but she has a point there. Merle gene makes the effect of
any white spotting genes much stronger. When a dog is MM SS (homozygous
solid, homozygous merle) its white patterns varies from no white at all to
lots of white, perhaps up to solid white. At least a Dachshund book I have
read says so, and it was written here in Finland where there are no piebald
Dachsies, just solids.
As the amount of white on MM SS dogs is probably at least partially
controlled by genes, in theory it should be possible to breed for less
white. That requires generations of double merle to double merle breedings
and careful choosing. I don't know if all white could be bred out like
this. And could deaf or blind dogs be totally avoided? I don't recommend
trying, but if somebody has anyway already done that, it would be
interesting to see the results. And not just the best dogs, but all pups
from all litters.
> I don't recall seeing white factoring mentioned except in the context
I have seen it mentioned, but naturally I can't remember where.
> My understanding of the MM effect is that it can completely inhibit
> pigment development- IOW, create white- in an area that would be diluted
> (merle) if the dog were Mm, and fully colored in a mm dog.
Hmm, not exactly. Harlequin gene does just that: it turns the grey coat
parts of normal merle into white or nearly white. Merle gene itself adds
some white, but it does it more by making the white coat patches caused by
other genes bigger and more irregular. It can add some extra white here and
there, and there really seems to be more white "over" the coat areas which
are grey and not black. But double merle dogs have merle or grey coat
patches, not black, which would be the case if all merled coat areas would
have turned into white.
Liisa
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| Christy |
"Sionnach" <rhyfelwr@msn.com> wrote in message
news:2jdr94Fvt6reU1@uni-berlin.de...
> Second thing- she appears to be claiming that the deafness/blindness
seen
> in homozygous merles is due to the white factor gene also being present,
> and/or that the MM effect doesn't occur if you're breeding solid merles
> (i.e. merles with no white markings). Is this the case?
> It's not how I've understood anything I've ever read on the MM effect; I
> don't recall seeing white factoring mentioned except in the context that a
> heavily white factored Mm and a MM may LOOK similar (IOW, be primarily
white
> with small merle patches).
>
> My understanding of the MM effect is that it can completely inhibit
pigment
> development- IOW, create white- in an area that would be diluted (merle)
if
> the dog were Mm, and fully colored in a mm dog.
Has she bred merle to merle yet?
I would be very suprised if she bred a solid merle to a solid merle and
ended up with solid merles, unaffected by white and thus without
vision/hearing issues.
From what I've seen of double merle shelties, the amount of white on the
parents doesn't have any bearing on the amount of white on the puppies -
some end up mostly white, some end up with colored spots. When the white is
in the eye or ear area, those are generally defective. So while I certainly
don't think its a good idea to TRY, if she's doing it anyway, I'm curious to
know the results, and if her puppies end up with signifigant white and/or
vision/hearing defects.
Christy
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