The Roslin Institute

Public Interest

Cloning

The Roslin Institute no longer undertakes research related to cloning of animals, although many of the techniques developed as part of the research that resulted in the birth of Dolly the Sheep continue to be used in the Institute's development of genetic modification technologies and applications.

Most of the scientists who undertook cloning research at The Roslin Institute, including Professor Sir Ian Wilmut who headed the group whose work led to Dolly, have moved on to work at different organisations. However, if you are interested in the subject of cloning animals we have produced a series of Cloning FAQs that might interest you.

If you have specific questions relating to the field of cloning or to the production of Dolly the Sheep please see the Additional Links below.

FAQs

Q. What is the current method(s) of cloning?
A. 'Dolly the Sheep' was cloned using Somatic Cell Nuclear Transfer and this is still the foremost method of cloning used. Several minor modifications (e.g. using chromatin modifying agents) have been tried but there has been no real advance on the method used to produce 'Dolly the Sheep'. Importantly, the efficiency has improved significantly, which means fewer animals are used.
Q. What are the potential scientific and medical advancements made through research on cloning?
A. The major advance was to show that cells could be reprogrammed to function as a different cell type. This provided an important impetus for stem cell research, which is now being evaluated for human medicine. A recent and exciting development has been the generation of iPS cells. Cloning research provides vital information about how to change the function of a cell.
Q. What are some specific defects that cloned animals have been or could be born with? Are the reasons for the defects known?
A. Cloned animals have, in some cases, displayed growth defects although exactly why is not known. The growth defects are probably a result of the in vitro culture conditions and due to changes in chromatin in the nucleus but further research would be required to fully understand this.
Q. Are there any animals that have proven more difficult or impossible to clone? If so, why?
A. Rats and rabbits have been difficult to clone, but the reasons for this are not known.
Q. When cloning an animal, is it possible to alter the genetic code kept in the nucleus to produce particular results?
A. Cloning itself does not alter the genetic code. However, donor cells can be genetically manipulated in vitro and then cloning used to make a GM animal.
Q. What kind of cloning (cloning of plants, animals or humans) is mostly used?
A. Animals
Q. Are you allowed to use therapeutic cloning in certain situations, such as to save a child with a disease?
A. No. there is research in this area (at organisations other than The Roslin Institute) but this is rapidly being overtaken by the opportunities that induced pluripotential stem cells (iPS) offer. Stem cells are the primitive cells that have not yet been triggered to become a particular cell type. iPS cells are tissue-specific cells that have been chemically induced to return to a pluripotent state, i.e. they are once again able to be directed to become any cell type.
Q. If it is "wrong", why did they develop cloning?
A. Cloning (or to give it its proper name Somatic Cell Nuclear Transfer) was developed to enhance the ability of science to produce genetically modified (GM) animals. Currently the technique is used to produce GM sheep, pigs and cattle. It has subsequently found use in some animal breeding strategies and there are companies pursuing this to enhance certain (not all) livestock breeding strategies. So for some situations cloning can be "right", i.e. for some animal breeding. Roslin’s Director at the time Dolly the Sheep was born stated that "the genie was out of the bottle". It is not easy to see into the future; before the Roslin Institute did the cloning experiment no one knew if it would work of not (this is the art of science) - the minute after 'Dolly' was born it became history.
Q. What are the strongest reasons for why most countries have banned cloning?
A. Not all cloning is banned; animal cloning is allowed. Cloning of human beings is indeed banned. The technical use of cloning is limited by the poor success rate. Biologically, cloning is limited in that all you are doing is producing a copy of a current animal.
Q. Are there countries, where cloning (therapeutic/reproductive) is allowed? And how is it going there? Did it cause any problems?
A. All claims for human cloning are in the media and we at The Roslin Institute only know what it reported therein. In respect to animal cloning, there is a growing mass of scientific literature showing that clones and food products from them are as safe as non-cloned animals and foods.
Q. If there weren't any politicians, and the researchers could allow cloning, do you think that the researchers would allow it?
A. "Researchers" are citizens like any other member of the public; they consider their research and the ethical and moral implications of it as would anyone else. So like society at large some scientists would authorise the use of cloning and some would not.
Q. What comments would you like to add in relation to cloning?
A. cloning has done two huge things:
  1. It has opened up the field of reprogramming (of a nucleus' genetic material) which provided the impetus for the rapid expansion of stem cell biology and the promise of new stem cell therapies to help mankind.
  2. ii. It has brought biology into the everyday life of the public. As a direct result of 'Dolly the Sheep' our society is more informed, has more opinions and has more influence on how science is done and applied.
Q. Occasionally one hears claims that extinct animals (e.g. woolly mammoths, Tasmanian tigers or dinosaurs) are going to be brought back to life using somatic cell nuclear transfer using frozen or otherwise preserved tissue and surrogate pregnancy in related animals. How plausible are such claims?
A. Although in theory such "resurrections" might be possible, in reality they are extremely unlikely; there are two BIG issues.
  1. First, a suitable surrogate mother animal is required. For the mammoth this would need to be an elephant (as best biological fit) but even here the size difference may preclude gestation to term. For a Tasmanian tiger this would need to be another large species of marsupial which will poss quite a challenge. It is possible that closely related species could be utilised but it should be noted that no one has managed inter-species cloning yet. There is certainly no dinosaur-friendly recipient; our biggest reptile is the alligator, which is just not big enough, and we have no idea if reptiles can be cloned - only mammals have been cloned. There is very little known with regards to the embryology of such wild animals so our ability to perform experimental embryology including cloning would at the very best be extremely inefficient. For livestock we predict efficiencies in the range of 1-5%; for a wild animal at best we might aspire to 0.1%, i.e. 1 live animal from 1,000 transfers.
  2. Secondly, for cloning to work, viable whole cells are required. So for example, the mammoth tissue frozen in Siberian tundra may not be suitable. Yes if there are intact cells in this tissue they have been 'stored' frozen. However, if we think back to what actually happened to the animal - it died, even if from the cold, the cells in the body would have taken some time to freeze. This time lag would allow for breakdown of the cells, which normally happens when any animal dies. Then the carcass would freeze. So it is unlikely that the cells would be viable. Even, let's say that one in a thousand cells were nevertheless viable, practical issues come into play. Given that we have an efficiency of 1% cloning for livestock species (we have no idea how difficult it will be from this species - some living species have proven extremely difficult to clone, e.g. rabbit and rat) and if only 1 in a thousand cells are viable then around 100,000 cells would need to be transferred. Given the comments above, only cattle could be the recipient surrogate mother for a mammoth, and each surrogate could realistically only carry one foetus. So we would need 100,000 cattle for this experiment. The prediction of a one in a thousand viable births is most likely to be an underestimate and given the inefficiency of embryology methodology as indicated above all indications are that this experiment would be vast and beyond practical funding possibilities (many, many millions of £s). For animals where preservation has not been instant leading to poor cell quality cloning is not possible.
Q. If an extinct animal, e.g. a mammoth, was successfully brought back into being, can we really say that a mammoth has been recreated given that the animal's mitochondrial DNA will have come from the surrogate?
A. Given that the animal would be a hybrid of genomic and mitochondrial DNA it would not definitively be the intended animal (mammoth in this example). There are experimental strategies that could be employed to optimise the uptake of the donor mitochondrial DNA but these are only partially successful. Of note it is predicted that the mitochondrial DNA would degrade quicker than the genomic DNA so adding a further limitation on finding viable cells.

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