# Puppy DNA/Identical twins



## Jax's Mom

I've always wondered how much DNA varies from one littermate to the other? Assuming the same sire for all litter mates.
With human identical twins, if one set has children with another set, their offspring are technically (genetically) brother and sister, not cousins, because their parents have interchangeable DNA.
Do identical twin puppies exist? Has anyone ever even checked for this?


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## Catu

Half brothers and sisters... unless the twins share spouses.

Yes. I have thought about that because my father has a twin brother. If some day I need a bone marrow donor... I'll contact my cousins, though with the half sisters my father had been spreading around it should be enough.

Twin puppies does exist. I remember hearing a breeder talking about witnessing them. She didn't need a DNA test because she was assisting the birth and she herself removed both puppies from the same sac.


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## CLARKE-DUNCAN

I don't really know thats a really good question! Probably anything is possible!


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## onyx'girl

There is a recent thread going on another board on this subject, I thought it was interesting!


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## vomlittlehaus

Same sac they would be identical twins. If you were to study reproduction, you learn when fertilization occurs and cell division starts. Human identical twins are born in the same amniotic sac. One egg divides into two. Some times humans ovulate two eggs and they are fertilized, these are not identical and each has its own sac. I am not positive, but I would think it would be the same in dogs. Same sac, identical. When the chromosomes start dividing and forming pairs they determine characteristics of each pup. I am sure several of those pairs are the same, but not all. The canine has 76 autosomal and 2 sexual chromosomes. When the zygote(first cell) forms at fertilization that is where all the chromosomes already are. If that zygote splits in two you have an identical twin. Unless a mutation occurs after the split.

I am tired and fighting a sinus infection, and rambling. Sorry.


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## PupperLove

This is an interesting question, and I have also wondered about it. But I do believe it's possible. My friend has a dog who is a mixed breed, some sort of husky mix- she looks like a mix of husky, greyhound, and gsd if I had to fathom a guess. I saw another dog that was absolutley idenctical to her, which is so strange considering her unique look. EVERYTHING looked the same on this dog, which was also a female. Everything from her build, to coloring, to markings- a very subtle white tip on her tail...to the way it curled and the size and set of her ears-which would be understandable with a purebred dog, but a mix? It was really interesting, and shocking to see!


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## Emoore

Jax's Mom said:


> I've always wondered how much DNA varies from one littermate to the other? Assuming the same sire for all litter mates.
> With human identical twins, if one set has children with another set, their offspring are technically (genetically) brother and sister, not cousins, because their parents have interchangeable DNA.
> Do identical twin puppies exist? Has anyone ever even checked for this?


The biology of siblings is the same whether you're talking about animals that have litters like dogs or animals that have solo offspring like humans usually do.

Regular littermates, assuming the same sire, are genetically the same as a regular brother/sister or fraternal twin. A different sperm/egg pair for each puppy/sibling. 

I'm sure identical twin puppies do exist. It would happen the same way it happens with humans: after the egg is fertilized, it splits into two zygotes, creating two genetically identical individuals.


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## Jax's Mom

I was more curious about whether or not it was possible for canine eggs to split and survive? I don't see why not, but evidently the canine genome hasn't been mapped out enough to actually prove identical twins exist at all. 
I read somewhere that there is another type of twin that's a "half identical" twin where the egg splits and the twins become genetic clones of the mother/father. 
I thought it might be interesting for breeders to know if one if their exceptional dogs had a clone around somewhere that could also be bred...


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## Emoore

Jax's Mom said:


> I read somewhere that there is another type of twin that's a "half identical" twin where the egg splits and the twins become genetic clones of the mother/father.
> .


If I'm understanding what you're talking about, it's not possible, since each egg cell and sperm cell only has _half_ of the parent's genes.


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## carmspack

I did have identical twin pups -- took them out of one sack and took a picture of them on the blanket with a Y shaped umbilical cord still attached . Two points , one to each pups belly twisting together to end up as one cord . 

Carmen
Carmspack Working German Shepherd Dogs


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## onyx'girl

carmspack said:


> I did have identical twin pups -- took them out of one sack and took a picture of them on the blanket with a Y shaped umbilical cord still attached . Two points , one to each pups belly twisting together to end up as one cord .
> 
> Carmen
> Carmspack Working German Shepherd Dogs


Did both pups survive? If so, was there any health issues that you are aware of? From reading the thread on the PDB, many identical twins have one that doesn't thrive.


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## carmspack

both survived, no issues . I didn't think it was that unusual . Surely twins must happen that we aren't aware of or not present at moment of birth. They were only fractionally smaller than the other littermates . The dam was a female that routinely had litters of 12 pups per whelp. I've wondered in situations where you have one pup arriving within minutes of another if they were not twinned , which was not unusual for this female . Literally minutes later another would arrive . Sack already broken so who knows ? It just so happened that this one set arrived still in the sack , at first I thought it was a placenta , till I moved it away and saw the pups nose to nose through the stretched sack, broke it open at the head end and then pulled the placenta out of the way to take a picture of the pups face to face with umbilical cords still attached. Then I got out of the way and let mum dog take care of them. No problems - didn't pay any more or less attention to them as any of the other dogs in the litter , just didn't think it was that unusual . There was nothing to differentiate them . In the end I wouldn't even know which ones they were by the time they left . 
Carmen
Carmspack Working German Shepherd Dogs


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## carmspack

I should have said they were only fractionally smaller than the littermates AT BIRTH, within days of sucking away they were lost in the crowd.
Carmen


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## Catu

carmspack said:


> I did have identical twin pups -- took them out of one sack and took a picture of them on the blanket with a Y shaped umbilical cord still attached . Two points , one to each pups belly twisting together to end up as one cord .
> 
> Carmen
> Carmspack Working German Shepherd Dogs


Do you still have that picture? I would LOVE to see it!

Jax, at the end, every litter-mate is an "half-twin" as we are with our brothers and sisters, but as Emoore pointed, it is impossible to have such mother and father clones because gametes only have half the genetic information of each parent.


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## Jax's Mom

There is a genetic mutation where monozygotic twins (identical twins) can become a male/female set, which is what I was referring to as "half twins".


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## carmspack

I have the picture somewhere in a shoe box -- this was pre digital cameras . If I find it I will scan it and share. Not much to see, two newborns facing each other, still wet , with the umbilical cord(s) , earlier born littermates in background.
Carmen


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## marshies

Jax's Mom said:


> There is a genetic mutation where monozygotic twins (identical twins) can become a male/female set, which is what I was referring to as "half twins".


I don't understand canine biology, but from my understanding of human biology, they would not be identical twins. Identical twins share 100% of their chromosomes, including their sex chromosomes. Males and Females are differentiated at the 23rd pair of chromosomes in humans. They would then be fraternal twins and share DNA like siblings do.

In terms of having the exact DNA of the parents, from my understanding of Meiosis in humans, it is not possible. When humans make egg and sperm cells, they first have a diploid cell that contains 2 copies of the genetic information. They are recombined to form 2 unique cells that each have a special combination of a full set of chromosomes. These 2 cells are then split into 2 each, without further duplication of DNA material. The end result is 4 cells with only half a set of chromosomes each. All 4 cells have a unique set of chromosomes. 

When sperm and egg meet, they join the 2 sets of half chromosomes to form the unique genome of the child.


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## CuriousKira

I am a nanny to twin boys & have wondered this myself about dogs. 

carmspack do u happen to still have the picture, I'd love to see that!


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