Behind the few successes of cloning are many failures that you might not hear about. Even when a cloned animal is successfully born, problems can develop later in its life, and short lifespans make research difficult to conduct. Although cloning might have benefits, it also involves many risks and costs. Cloning is an expensive procedure that provides little result for a lot of work.
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High Rate of Failure
More than 90 per cent of attempted clonings fail, and it might take 100 or more nuclear implantations to produce a viable offspring. Failure in the cloning process can occur for a number of reasons, including an incompatible egg and nucleus combination, failure of embryo implantation into the mother or a failure in the pregnancy itself.
Poor Health and Early Death
Cloned animals tend to have a lower-functioning immune system, increasing their likelihood to develop infections, tumours and other disorders. Clones generally do not live long enough to provide enough data concerning how they age, and appearing healthy at a young age is not a good indicator of lifespan. According to the Human Genome Project website, the first sheep cloned in Australia appeared to be healthy until the day she died unexpectedly, and her autopsy did not reveal a conclusive cause of death.
Cloned animals are often much larger than their counterparts. This is called Large Offspring Syndrome (LOS). Their enlarged organs cause problems with breathing, blood flow and other functions of the body. LOS does not happen in every case, and scientists cannot predict when it will happen. Even clones without LOS can suffer from kidney and brain malfunctions and develop problems later in life.
Differences in Telomere Length
Chromosomes of cells get shorter as the cells divide. This is because the telomeres, DNA sequences at both ends of a chromosome, shrink in length with each copying of the DNA. The older an animal is, the shorter these will be. This is a natural part of ageing. The chromosomes from cloned animals have longer telomeres than normal, showing signs of youth and seeming to have an extended lifespan. However, this is unpredictable, because according to the University of Utah Genetic Science Learning Center, Dolly, the first cloned sheep, had shorter telomeres than usual.
In naturally created embryos, DNA is programmed to express a certain set of genes and this program changes as the embryonic cells begin to differentiate. A cloned nucleus does not follow the same program as a natural nucleus, and it is up to the scientist to reprogram it. Incomplete programming causes the embryo to develop abnormally. According to the Human Genome Project website, researchers at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, discovered that about 4 per cent of the genes in cloned mice functioned abnormally. The abnormalities were not caused by mutations in the genes themselves but by changes in the normal expression or activation of certain genes.
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