breading a Blue Merle Rough Collie

Question
I have a two year old Female Rough Tri Collie (Caylor). I also have a one year old male Rough Sable Collie (Jackson). I have always wanted a Rough Collie Blue Merle. Is it better to bread a Tri with a Blue Merle or a Sable with a Blue Merle? what would you get breading a Sable with a Tri, i mean, is there a chance of a Blue Merle.

Please excuse my ignorance on the matter.

Many Thanks

Keith

Answer
Hi Keith

Not ignorance, coat color and genetics is complicated and can be mind numbing.

Just to explain, merling is caused by an incomplete dominant gene. Patchy dilution, black becoming patched with gray ('blue merled') or sable becoming sable merle. Merling also affects the eye color.

Most merled dogs are actually the heterozygote, Mm. There is good reason for this; there are serious health problems associated with the homoygote MM, including tiny eyes (microopthalmic) or even entirely missing eyes (anopthamlic). The homozygote is also known as a 'double merle'. They are often predominantly white, hence their alternate name 'defective white'.

When breeding merles, many reputable breeders avoid breeding Mm to Mm; they generally go for Mm X mm and get 50% single merles (Mm) and 50% not.

It all comes down to what genes are the dogs carrying. If you aren't going to do testing, do you know the lines of the dogs. What did the parent, grand parents and great grand parents on both sides look like?