The Big Question: Could cloning be the answer to saving endangered species from extinction?
Tuesday 03 February 2009
Why are we asking this now?
An extinct species of mountain goat called the Pyrenean ibex, or bucardo, has been "resurrected" by scientists who had managed to create a clone of it with the help of domestic goats. Unfortunately the resurrection was short-lived as the new-born kid died with minutes of being born owing to breathing difficulties caused by deformed lungs. However, the feat was a first in that no one had previously managed to create a clone of an extinct species.
How did they do it and why?
The scientists, led by Jose Folch of the University of Zaragoza in northern Spain, wanted to see if they could in some way preserve the genetic material of the bucardo. They had taken skin cells from the ear of the last bucardo known to have lived, a female they called Celia. The sampling took place in 1999 and Celia was subsequently released. However, in January 2000 she was found dead next to a fallen tree with her skull crushed. Folch and his colleagues had carefully stored Celia's skin cells in liquid nitrogen at about minus 196C.
Over several years, they undertook a series of cloning experiments involving the transfer of the cell nuclei containing the bucardo's DNA into a batch of "empty" egg cells from domestic goats, a close relative, which had their own nuclear DNA removed. This is the standard way of producing a clone using the "cell nuclear transfer" technique that led to the creation of Dolly the sheep. The one big difference, however, is that in this case the resulting embryos were "hybrids" of goat eggs and bucardo skin cells, and instead of transferring the embryos back into a female bucardo – there were none available – the scientists used the domestic goat as surrogate mothers.
How efficient is the process?
The cloning process is still very inefficient, even when done between members of the same species. When, in 1996, Dolly was created from the udder cell of a female sheep, it took 277 attempts to produce just one live, healthy offspring – Dolly. This bucardo experiment was even more inefficient, which is to be expected given that it involves fusing cells from different species. An earlier attempt to clone the bucardo ended in failure in 2003, with just two pregnancies from dozens of attempted embryo transfers. Both pregnancies did not get beyond the two-month stage. In the latest attempt, the scientists had created 439 ibex-goat hybrid cloned embryos. Of these, only 57 were deemed suitable for transfer into surrogate goat mothers. And of the seven pregnancies, just one gave birth to a live offspring.
Was there always a risk that the bucardo might not survive very long?
It is well established that cloned animals often suffer from developmental problems. Very often these problems prevent the pregnancy from continuing normally, and sometimes the cloned offspring that do get born suffer health problems that either kill them in the womb or lead to later ailments in life. This is one of the reasons why some biologists are very concerned about the use of cloning to preserve endangered animals.
Are there any safer ways of cloning animals?
There is a very new method being developed called induced pluripotent stem (iPS) cells. As the name implies, it is a way of creating embryonic-like cells from ordinary skin cells by tinkering with a handful of genes. But scientists have demonstrated that the embryonic stem cells created by the iPS method can also develop fully in the womb just like ordinary embryos and result in live births.
And what's the eventual aim?
The aim eventually is to refine the technique so that, for instance, the skin cells of an endangered animal are genetically manipulated in the laboratory to create iPS cells that can then be made into cloned embryo for transfer into the womb of a surrogate mother. A number of groups are looking into this as a possible alternative to Dolly-like cloning for endangered animals.
Are there risks in this?
There is again some evidence that the offspring created by the iPS technique may not be entirely normal. Cloned mice produced by the iPS method, for instance, do not seem to live as long as ordinary mice. This would have to be taken into account before it is used on bigger animals that are rare or endangered.
Why do scientists want to clone endangered animals?
They believe that cloning offers another way of preserving the unique genetic identify of a rare species in the body of living animals that could be used for breeding purposes. Some endangered animals are so rare and so difficult to breed in captivity that cloning offers a viable alternative route to continuing the genetic line, especially if surrogate mothers of a closely-related, non-threatened species are used.
Which animals are the object of attention?
There are at least half a dozen serious projects to investigate the possible use of cloning to preserve some of the world's most threatened species. The animals being considered range from the giant panda and the Sumatran tiger, to the African bongo antelope and the pygmy hippo.
There have already been clones of endangered animals. The most famous was Noah, a baby gaur, a wild ox-like bovine from south-east Asia, which was cloned using the eggs and surrogate wombs of domestic cows. Unfortunately, Noah died within the first 48 hours of being born due to an intestinal infection that may have been made worse by the fact that he was a hybrid clone of a gaur and a cow.
More recently, scientists have had more success with the European mouflon, a rare breed of sheep found in Sardinia, Corsica and Cyprus, which was cloned in 2001. In 2003, a separate team of scientists cloned another type of wild cattle called a banteng, using cow eggs and surrogate mother cows.
So is cloning the answer to the problem of endangered animals?
Almost certainly not. The biggest threats to wild animals today are habitat loss, human encroachment, poaching, pollution and climate change. Almost everyone involved in the conservation of species would put tackling these problems far higher up the agenda than cloning.
Many experts go further and say that cloning is a harmful distraction from the main job of the preservation of the wilderness, which is being lost at an astonishing rate, along with the animals and plants that live there.
However, there is a case that under certain circumstances, and with certain species, cloning could be a useful tool for preserving the genetic material of an endangered species on the verge of extinction.
It could be especially useful for animals whose genetic diversity is already limited or dwindling. But no one who knows about threatened species believes it is the panacea that could curb the mass extinction of animals and plants currently taking place on the Earth.
Should the cloning of endangered animals be allowed?
*It offers a possible route to saving the unique genetic make-up of a species in the body of a living creature
*The cloned offspring could be used for captive breeding to boost wild populations
*It does no harm to wild populations if another species can be used as surrogate mothers
*It offers no real solution to the most pressing problems faced by endangered animals, such as habitat loss
*It is potentially dangerous in that it gives the wrong impression that a species can be saved
*It harms the animals involved and creates a form of inbreeding that could be detrimental to the species
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