back from the dead? not exactly

In one of my classes we talk a bit about cloning, in the context of discussing various biotech techniques and their applications. Sometimes someone asks if I'd clone my dog (or my husband!) after they'd died, & my response is always to say 'no'. Not because I don't love them both (husband much more than dog, he'll be glad to hear!), but because I know that whatever I got, it wouldn't be the original being. 

So when this story popped up in my newsfeed, I thought to myself that it would make a useful starting point for class discussion – after all, 'Dead dog lives on after British couple pays to clone him back to life' does have a certain morbid appeal to it. But my own answer would still be 'no'. For several reasons (none of which are mentioned in the original news story).

First up, the dog isn't going to be an exact genetic replica of the original. This is because the technique that was used involves implanting the nucleus of one of the dead dog's cells into a donor egg that's had its own nucleus removed: the nuclear DNA will be that of the original dog, but the mitochondrial DNA – in the egg, and in all subsequent cells – will come from the egg donor. This is because mtDNA is passed on almost exclusively down from mothers to children. And since mitochondria play a role in other cellular functions besides production of ATP, then this potentially affect the phenotype of the new organism.

In addition, the dog developed as a foetus inside a host mother: the intrauterine environment would not, could not, have been the same as that in which the original dog developed. Because these different environments can have different effects on how the information coded in DNA is expressed (a phenomenon known as epigenetics), it's again quite possible that aspects of the new dog's phenotype could be changed in subtle and unpredictable ways. 

And a third consideration is this: the fail rate of cloning is far greater than its success. According to this page on the University of Utah website

Cloning animals through somatic cell nuclear transfer is simply inefficient. The success rate ranges from 0.1 percent to 3 percent, which means that for every 1000 tries, only one to 30 clones are made. Or you can look at it as 970 to 999 failures in 1000 tries.

That's a lot of donor eggs (the collection of which involves a certain amount of risk), and a lot of host mothers, to get a single dog – a dog that will not, cannot, be exactly the same as the original. Biologically, ethically – personally I would not go there. I'd rather mourn, remember with love, and move on.


One thought on “back from the dead? not exactly”

  • Aside from the genetic differences, the original article didn’t mention the cloned animal would also be different behaviorally. We, and dogs, are also a product of the environment we are raised in. Unless you replicate the same environment, the person, or dog, will certainly have different behavioral traits. Even if you manage to replicate the environment, there is no guarantee the resulting behavioral traits will be the same. Wasn’t this the plot of “The Boys From Brazil” movie starring Gregory Peck and Laurence Olivier?

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