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Animal cloning is a reproductive technology that uses the genetic code from one animal (the ‘parent’), to produce another animal (the ‘clone’) that is almost the parent’s exact physical replica. This technology uses deoxyribonucleic acid (DNA), the basis of the genetic code, located within individual animal cells, in a structure called a nucleus.
The technique most commonly used for cloning is called somatic cell nuclear transfer (SCNT). The term “somatic” refers to any body cell other than a sperm or an egg cell. SCNT was used to produce “Dolly the sheep”, the first animal cloned from a somatic cell taken from an adult animal. In this technique, the nucleus of one somatic cell from the animal to be cloned (the donor animal) is removed and the rest of the cell is discarded. At the same time, an egg cell from another animal also has its nucleus removed, however, in this case, the enucleated egg cell is retained and the nucleus is discarded. The nucleus from the donor animal is inserted into the enucleated egg cell, and, with the help of an electrical pulse, the egg cell will begin to divide and grow into an early-stage embryo. Success rates for SCNT technology are low. If the embryo develops normally under laboratory conditions it is transferred after a few days into the uterus of a foster mother where it develops until birth.
Animals produced using SCNT are not exact genetic copies of the donor animal. A very small amount of DNA is present outside the nucleus in other cell structures called mitochondria. The clone carries DNA from the nucleus of the donor animal, but also obtains genetic information from DNA in the mitochondria of the enucleated egg cell.
Cloning in Livestock Production
Researchers are investigating the potential of using animal clones in livestock production. Cloning allows breeders to select animals with desirable traits and have them reproduced in the offspring. Selective breeding using traditional practices (encouraging two animals to mate) does not always result in offspring with the desired traits.
Cloning could be used to select genetically desirable traits such as a dairy cow that produces milk with unusually high milk protein content, which is important in cheese manufacturing, or an unusually low saturated fat content, which presents potential human health benefits. Researchers have suggested that cloning could also be used to preserve a species nearing extinction or to enhance livestock resistance to illnesses, such as foot-and-mouth disease.
The ethical and moral implications of using cloning for livestock production have been a matter of debate. Concerns have been raised about the low success rate of the SCNT cloning technique and the possible reduction of genetic diversity.
Cloned Meat
In January 2008, a final risk assessment by the United States Food and Drug Administration (U.S. FDA) concluded that meat and milk from cloned animals are safe for human consumption. In July 2008, the European Food Safety Agency (EFSA) adopted a scientific opinion on the implications of animal cloning on food safety, animal health and welfare and the environment. A key conclusion of the opinion was that there is no indication that differences exist in terms of food safety for meat and milk of clones and their offspring compared to conventionally bred animals. Only pigs and cattle were addressed in the opinion.
Health Canada’s 2003 interim policy on cloned animals considers food from livestock developed using SCNT to be novel foods. In Canada, these products are subject to the Food and Drug Regulations (Novel Foods); thus, cloned animals obtained through SCNT, their offspring or by-products, including meat, eggs and milk, cannot enter the human food supply until a pre-market safety assessment has been conducted. The interim policy states that there has not been enough research to guide the pre-market safety assessment. Health Canada has stated its plan to continue with extensive research into the safety of products derived from cloned animals. The sale of these products is still prohibited in Canada.
Information Sources
European Food Safety Authority. (2008). Food safety, animal health and welfare and environmental impact of animals derived from cloning by somatic cell nucleus transfer (SCNT) and their offspring and products obtained from those animals. Retrieved from http://www.efsa.europa.eu/EFSA/efsa_locale-1178620753812_1211902019540.htm
Health Canada. (2003). Food directorate interim policy on foods from cloned animals. Retrieved from http://www.hc-sc.gc.ca/fn-an/legislation/pol/pol-cloned_animal-clones_animaux-eng.php
National Academy of Science. (2002). Food safety concerns. In Animal biotechnology: Science based concerns (pp. 61-72). Retrieved from http://books.nap.edu/books/0309084393/html/61.html
U.S. Food and Drug Administration. (2008). CVM and animal cloning. Retrieved from http://www.fda.gov/cvm/cloning.htm
Wells, D.N. (2005). Animal cloning: problems and prospects. Revue scientifique et technique (International Office of Epizootics), 24, 251-264.