I've wondered about identical twin pups, whether it was possible, whether they would be marked identically (considering that basically one gene - unless you count Tw, but that's rare - produces such diverse patterning in merles, and the various patternings that dogs with the same genes for white spotting can have). I was interested in whether the variation was due to the influence, at least in part, of other genes than the main ones we know about yet or whether uterine environment for eg was an influence.

Just found this http://www.ashgi.org/color/twins.htm about merle twin Aussies, which I think is interesting. The pups shared a placenta and amniotic sac, so are known to be twins, but have some interesting variations in things like depth of tan colouring (which I am pretty sure has been thought mainly genetic in origin), distribution of patches and white spotting. Unfortunately the pics only go up to 4 wks, would be really interesting to see them as adults.

i have not had the chace to read it yet but those pups are just so cute and coming out of the same sack they have got to be twins

They are pretty little things, aren't they? But I think that if you saw them, you wouldn't guess they were twins. Twins might be more obvious in short haired breeds when they were adult, I guess - the long hair obscures seeing their bone structure.

It's interesting to think that even though twins may be genetically identical, their markings may be dissimilar. The variation in the dark patches and the tan colouring makes me think that there must be something in utero that also has an effect on the way the colours develop across their bodies. I guess even identical human twins whilst to the casual observer may look identical to those that know them well there may be "obvious" differences. I've only ever known fraternal twins. But I'm fascinated by mirror twins!

I read an interesting article a while back about cloning horses, if a pinto horse was cloned, it would be identical BUT the markings couldn't be controlled...as the gene tells that there is white/solid but doesn't control where & it was random during development....so whilst the results could be full clones the markings may not be identical.

I know there was a debate about this as by basic terms a full clone should be an identical replica of the initial, but the scientists argued it due to the gene not controlling where the markings occur only their presence.

I wonder if this relates to the twins having different markings??? theoritically

Yes, I think it is similar. I know that tortie cats have a similar thing going on, that genetically identical animals are differently marked. I'm not really that sure of how patterning occurs in the skin and coat in detail, but I do know that in torties o is active in some cells, and O is active in others, and whichever is the case determines the colour of that bit of the cat. The processes that determine what is active where don't seem to be genetic, they seem to be environmental.

I guess with identical twins you have the complication that the pups are not only genetically identical, but have developed in a very similar environment (in the same amniotic sac). The person who wrote this Aussie page thought it was significant that the pups although they didn't have exactly the same markings, had similar amounts of merle-dilute. But I reckon you'd have to see lots of others before you could tell whether that was a consistent thing or just chance with these two.

The answer to that may have implications on the question for breeders who believe the more coverage of colour on the parents (particularly the face and head location) the less chance of breeding to deafness with selective MM/MM or MM Mm matings.

In regards to the amount of white spotting, which some ppl think is significant in regard to producing MMs, then I think it would be the potential of that combination of parents to produce sisi pups that would be most important. I guess it's not surprising that many breeders look at a potential parent and think that its pups will have a similar amount of spotting to it. When it may well have the potential to produce much more white spotted pups than itself. If they mated 2 dogs that were Ssi, and who might not be phenotypically obvious as such, or an Ssi and an sisi then there is a good chance they would produce sisi pups. Environmental factors might make a difference in the details of whether a nose blaze goes on one side of the face of the other or how high the socks go etc, but basically the amount of white is probably determined genetically.

My view is that Mm x Mm is always a gamble. And that when things go well with it you can never be sure whether it was just luck or something about that pairing that 'avoided' producing MMs with abnormalities.

with the Mm x Mm matings you always run the risk of abnormalities but i know of breeders that have been doing these mating for many yrs and have only ever had the odd pup born with problems yet some poor buggers try this once and get sometimes half a litter that have abnormalities of one kind or another, so it makes you think why are some lines safe and others are not maybe it was because ??? lets say a heeler was crossed into one blood line back in the 1930's we don't have a record going back that far so it's possible and this is the one that has many more abnormalities born into it's lines we re's the safer line has no heeler crossed into it but has only had kelpies or borders mixed in. now i am only using these breeds as a suggestion, who's to say what's been mixed into our dogs back in the early years as every farmer was after a different type of worker one to head stock one to push stock what ever there needs were back then, no koolie is purebred farmers did not care what went into their dogs as long as they worked and did the job. thats why koolies from different parts of the country look different from each other i have some here that look like kelpies (Vic kelpie lines) in body shape but then again working kelpies from Vic look different from the working kelpies here in Q.L.D (and some that look like Q.L.D kelpies in shape)the ones that i have seen from Vic have longer legs and a lighter body then the kelpies here they are heavier in body shape and bone, see what i mean Vic kelpies are bred for sheep work Q.L.D kelpies are bred for cattle the farmers did this for a reason down south it's no good to have a heavy dog as it has to back sheep were a lighter dog can do this a lot better and quicker, and it's no good having a light bodied/ boned dog to work hard cattle as a good kick would see the end of it.