Science for Authors: Why Would You Clone A Dinosaur? #amwriting

By: Meradeth Houston on 4:00 AM

While I don't work with cloning in my laboratory, one of the questions I get asked all of the time is whether or not we'll be able to clone/revive extinct species. Jurassic Park movies of course play a role in this, and there has been plenty of other articles/books/TV shows that talk about the potential of bringing back extinct species.

So, first of all, when people think of this, most of the time it's the idea of bringing back mammoths, or dinosaurs, or something big and amazing from earth's history. But, really, there are a few other things to consider: many species have been driven extinct by human actions and bringing them back may aid in restoring the ecology of places that now no longer have a species that was necessary to fill whatever niche the extinct species filled. This has always struck me as a something that would be really amazing to do, as maybe we could help repair some of the damage humans have done to the natural world.

But, of course, that's not what most people think about :) Many would love to see a T-Rex in person (so long as they wouldn't be eaten!), and there are other cool things that would be awe inspiring. Here's the thing: with our current technology, we don't have access to the DNA from dinosaurs. Yep, even if it's stuck in amber. See, DNA degrades with time, just like the rest of our body. So the longer it's been since the organism was alive, the less "good" DNA that we can read is around. This makes any sort of ability to make say, a T-Rex, really hard.

There are other species, like mammoths, where we do have pretty decent DNA, as there have been nearly whole individuals locked in the permafrost and recently found. From these, though, we still have the issue of their DNA being degraded. It's like having a huge puzzle of billions of little pieces (the basepairs of A, T, C, & G that make up all our genomes) that have been broken into tiny pieces. Making sure all the pieces are there, and put back together in the right way, is not so easy. In reality, we don't have 100% of any mammoths genome to date, as there are always a few missing pieces.

This all being said, there are a few things that could be done to clone these species. These are still pretty theoretical, and contingent on a whole lot of other technicalities I'll touch on in a bit. But, what can be done is, if we're able to identify most of the differences in the pattern of A/T/C/G's in, say, an extinct mammoth, and a closely related elephant today, it's possible to edit the elephant's genome to resemble that of a mammoth. So, go in and switch the A in an elephant's genome to the T it is in mammoths. This could be done with the CRISPR-Cas9 editing system, although the number of changes are huge and the effectiveness questionable. The other way this could be done is through back-breeding. This is basically finding two individuals with a lot of the extinct species' DNA and breeding them together. The offspring would then potentially have even more of the extinct species' DNA, and through generations of this it would be possible to end up with an few individuals with most of the ancestral genome. But then there's always the question of whether or not all of the differences between the mammoth and elephant have been found, because the original mammoth copy of the puzzle isn't the best.

The other way this could be done would be to build the genome from scratch. This is a huge undertaking--billions of basepairs all linked together in the way that a mammoth's would be--but not too impossible in the near future. Again, so long as we have a good copy of the original.

Direct cloning will never work for any of these species. That's because, in order to do so, one needs an intact and healthy cell nucleus to transfer into another cell (and egg that has had its own nucleus removed), in order to have the cell start using the genome to build a body. No really old and dead species has an nucleus/genome intact enough to do this, as, again, they degrade after death.

Okay, so say someone does manage to get all the mammoth changes incorporated into a genome, gets it into an egg, and it starts to replicate and grow. Those hurdles are pretty crazy hard already, but then it's necessary to get that egg implanted into a potential mother, and have her carry it to term. Anyone who is familiar with IVF knows this is hard enough in humans when the cells are our own--doing so between two species, and especially with species who have complicated reproductive timing, is even harder. We even know now that modern human mothers probably couldn't carry to term babies made with a Neanderthal father--their immune systems were incompatible. And humans and Neanderthals are super close cousin species!

But, say this all works out. A mamma elephant has a baby mammoth. Then what? How ethical is it to have a single member of a long gone species hanging around, especially if that species is known to have been highly social? Where does this individual live, when it no longer has the vast frozen tundra to wander? Honestly, it makes me kind of sad to think about what this poor individual might have to endure.

Anyhow, this is all to say, that cloning of extinct species is possible. Maybe. Easy? Definitely not. Worth it? Maybe, as we could potentially help in bringing back, say, extinct species of Galapagos tortoises or Carrier Pigeons. But if you're really hoping for a pet Velociraptor sometime, it's probably (a) not happening anytime soon, (b) maybe not the most ethical of things to do, and (c) a good way to get eaten ;)