We humans have been accused of causing the extinction of a multitude of interesting animals, including the Dodo and my personal favourite the elephant bird , which once lived on the coast of Madagascar and is somewhat reminiscent of Kevin from the Pixar movie Up, but bigger. So if we are the cause of the loss of so many species is it our responsibility to try and bring some of them back? Scientists have been looking at the theory of de-extinction by cloning methods to see if we can produce some lost animals that could go on to become a population.
The science behind this method has been known for over a decade and used for a variety of uses. Nuclear Transfer, also known as nuclear cloning, produced the world famous sheep clone, Dolly. This technique is now being developed to treat inheritable mitochondrial diseases through ‘three-parent babies’. But how could it be used to re-introduce animals that have been gone for many years?
Nuclear transfer can only be used if there is preserved tissue from the original animal, with the cells intact. This is rare for most extinct animals but some tissues are still around, stored in labs or even being found buried under ice (like thewoolly mammoth remains found in Serbia last year!). Once these cells are isolated, the nucleus can be removed which contains the DNA and therefore all the information to produce a clone of the extinct animal. Dolly was produced by live sheep nucleus transplanted into a live sheep de-nucleated egg and an embryo grown before implantation into a pseudo-pregnant ‘surrogate’ sheep, which in turn gave birth to Dolly.
Scientists aiming to bring back animals from these preserved cells face two big challenges: the cells and therefore nuclei are long dead and the nucleus must be transferred to an egg from a different species, as there are no living members of the species to act as surrogates. In a study known as the Lazarus trail the animal to be resurrected was the gastric brooding frog and the scientists used eggs from another frog species and ran hundreds of repeats until one of the eggs began to divide. This showed that not only could related species eggs be used to hold the nucleus but that the molecules and proteins within the egg could somehow re-awaken the dead nucleus and cause it to transcribe and translate its DNA again. These cells produced an embryo and fingers crossed soon they will be able to implant this into a related frog and produce fertile gastric brooding frogs that have been extinct since 1981.
So perhaps it could be done and it definitely looks hopeful, but what about animals that died out hundreds or thousands of years ago? Can we clone a Woolly Mammoth? Well scientists within the Russian Association of Medical Anthropologists group believe that they now have enough preserved blood and bone to produce a Woolly Mammoth clone! If or when these experiments take place, they intend to use an elephant as a surrogate mother and possible even as a nuclear transfer egg donor (this hasn’t been clearly stated). This may cause further issue as the more distantly related the species the less likely it will be that the egg with the preserved nucleus will be able to form an embryo, but I’m certainly not saying it can’t be done.
If viable, usable DNA can be isolated from cells from extinct species then the beautiful and relatively simple method of nuclear transfer could prove a powerful tool in giving these animals another lease of life. There are of course numerous ethical issues with this and many groups accuse scientists aiming to do this as of ‘playing God’, in a debate that has been ongoing since Dolly first arrived on the science scene in 1996. Could it have an effect if we could produce animals that have been off the earth for such a long time? Should there be a decision on which we can and which we can’t? For instance if well preserved Neanderthal remains are found, would it be wrong to use a human egg and surrogate to bring back our evolutionary ancestors?
These are questions to be debated by people much cleverer than I. All I know is if there is ever get a chance to pet a baby Woolly Mammoth at a zoo or nature preserve; I will be first in line.
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Wilmut I (2003). Dolly-her life and legacy. Cloning and stem cells, 5 (2), 99-100 PMID: 12930620
Tyler MJ, Shearman DJ, Franco R, O’Brien P, Seamark RF, & Kelly R (1983). Inhibition of gastric acid secretion in the gastric brooding frog, Rheobatrachus silus. Science (New York, N.Y.), 220 (4597), 609-10 PMID: 6573024
Factsheet on Cloning, courtesy of the Roslin Institute