i heard that its not "done" to breed a sable to a merle,but only to breed merles to the tris.
why is this?could you get red merles if you did this?
or is there some other problem ?

im just being nosey,colour genetics are fascinating!

Some folks in Rough Collies breed sables to merles but the vast majority wouldn't.  Of course, as always with genetics, there's a mixture produced, but I've seen some very muddy looking blues and very grey dull looking sables from such matings. :(  And blues are the only colour where the colour is critical - apart from sables mustn't be too pale.

It's another reason why all 3 colours have different temperaments because, generally speaking, they have different blood lines!! :)

I think the upshot of it is, is that merle x sable can produce cryptic merles.  This is because merle needs eumelanin (dark pigment) to express and sables usually have very little of this.  They are born dark, so the merle pattern would be obvious in early puppyhood but when the coat clears, the pattern would not be so obvious though in shaded sables it should be.

Nothing wrong with cryptic merles healthwise, at least nothing more than normal merle (slight increased risk of eye/ear deformities) but as Val says, the pattern may not be too pretty for the showring.  Another reason not to breed cryptic merles (Mm) though, is that they could be mistaken for non merle (mm) and bred to a merle (Mm)  so producing homozygous merle at 25% risk.  These then of course have high risk of all the associated deformities.

Yes you could get brown (red:-) merles from merle x sable.  The sable would have to carry tanpoint (Ay at) or the merle parent would have to be dominant black (assuming we are talking about BCs?) to provide the dark pigment and brown would have to come from both parents.

Julie

Sorry, just noticed Sheltie in the topic :-)

Shelties do have black, at least in the states but it's recessive not the normal dominant black so ignore that bit.  "Red"...... not sure which red you now mean.  Shelties don't have brown do they?

Julie

This might help or not ;)

This is also interesting as it includes this
"M, merle. This is another dilution gene, but instead of diluting the whole coat it causes a patchy dilution, with a black coat becoming gray patched with black. Liver becomes dilute red patched with liver, while sable merles can be distinguished from sables with varying amounts of difficulty. The merling is reportedly clearly visible at birth, but may fade to little more than a possible slight mottling of ear tips as an adult. Merling on the tan points of a merled black and tan is not immediately obvious, either, though it does show if mask factor is present, and may be discernable under a microscope. Eyes of an Mm dog are sometimes blue or merled (brown and blue segments in the eye.)

Although merle is generally treated as a dominant gene, it is in fact an incomplete dominant or a gene with intermediate expression. An mm dog is normal color (no merling). A Mm dog is merled. But an MM dog has much more white than is normal for the breed (almost all white in Shelties) and may have hearing loss, vision problems including small or missing eyes, and possible infertility (Little). The health effects seem worse if a gene for white markings is also present. Thus the dachsund, which is normally lacking white markings, has dapples (Mm) and double dapples (MM) the latter often having considerable white, but according to Little other effects are limited to smaller than normal eyes. In Shelties, Collies, Border Collies, and Australian Shepherds, all of which normally have fairly extensive white markings, the MM white has a strong probability of being deaf or blind. The same is probably true with double merle Foxhounds and double merles from Harlequin Great Danes with the desired white chest. A few double merles of good quality have been kept and bred from, as a MM double merle to mm black breeding is the only one that will produce 100% merles.

It is possible that merle is a "fragile" gene, with M having a relatively high probability of mutating back to m. The observed pattern would then be the result of some clones of melanocytes having suffered such a back mutaion to mm while they are migrating to their final site in the skin, producing the black patches, while others remained Mm. This hypothesis also explains why a double merle to black breeding occasionally produces a black puppy, the proposed back mutation in this case occurring in a germ cell. On the other hand, the observed blacks from this ype of breeding may actually be cryptic merles - genetically Mm, but with the random black patches covering virtually all of the coat."