Animal Cloning: A New Frontier for Agricultural Biotechnology
Recent breakthroughs in the field of cloning have given rise to a myriad of scientific innovation, as researchers discover the potential of this technology. The goal of these endeavors is to find ways in which to apply cloning technology usefully, responsibly and constructively. Animal cloning holds the promise of innovating livestock breeding and of enabling significant advancements in medical research and treatments.
The Science of Cloning
A clone is a genetic copy of another living organism. Cloned organisms are produced asexually; sperm does not fertilize egg. Hence the genetic material of cloned offspring is drawn from a single source, rather than being a combination of sperm and egg genes. Many examples of cloning are found in nature. Certain species, such as shrimp and snails, regularly reproduce this way. In human reproduction, identical twins occur when an embryonic cell naturally splits in half. Each half contains the same genetic code. Artificial cloning attempts to achieve the same result through a variety of techniques.
Nuclear Transfer Techniques
Each cell of a living organism contains a 'blueprint' for its development. These instructions are composed of DNA which is located in the nucleus of a cell. Soon after an egg has been fertilized the cells of the developing embryo begin to acquire specialized functions, becoming, for instance, brain cells or skin cells. This is called cell differentiation. Once a cell has become differentiated, it never reverts to the prior undifferentiated state.
In the 1980s, scientists cloned a sheep embryo using a nuclear transfer technique. Two groups of cells were used in this process – one group of unfertilized eggs and one group of undifferentiated embryonic cells. The nuclei were removed from the unfertilized eggs (stripping them of DNA) and replaced with undifferentiated embryonic cells. This was done to transfer the embryos' DNA into the unfertilized egg cells. The embryonic clones created from this technique were then implanted in the uteruses of genetically unrelated sheep for the remainder of their gestation.
An elaboration of the nuclear transfer technique allows the cloning of mature organisms. This is done by placing the differentiated cells of the donor organism in a culture that causes them to return to their undifferentiated state before proceeding with nuclear transfer. "Dolly," a sheep produced in Scotland, was the first successful clone of an adult animal.
The production of Dolly was significant because this meant an animal with known properties, such as rate of growth and milk production could be cloned, whereas the productivity traits of offspring cloned from embryos remain unknown until these animals mature.
Dolly's Legacy: The Future of Animal Cloning
From nuclear transfer technology arises a range of beneficial applications. Among these are:
- More efficient production of transgenic animals: A transgenic animal has received genetic material from another species. On the horizon are transgenic cattle, goats or sheep (sometimes called "pharm" animals) whose milk contains therapeutic proteins which may be used to nourish premature infants or to treat emphysema, cystic fibrosis, burns, gastrointestinal infections, AIDS and other immunodeficiency diseases. Nuclear transfer cloning technology offers a more effective means of generating large numbers of transgenic animals which can produce potentially valuable pharmaceutical products.
- Animal health and medical research: Animals are often used as models for research. A large number of test variables can prevent scientists from determining the effects of experimental drugs, nutrition or housing conditions - cloning could help make such effects clearer by reducing variability factors.
- Xenotransplantation: This is the medical term for replacing diseased human organs with animal organs, a procedure made necessary by the chronic shortage of human organs available for transplantation. Nuclear transfer technology may enable additional genetic modifications in donor animals which would make these kinds of operations more viable.
For more information on biotechnology and animal cloning, contact:
Saskatchewan Agricultural Biotechnology Information Centre (SABIC)
c/o Ag-West Biotech Inc.
101 - 111 Research Drive
Saskatoon, Saskatchewan Canada S7N 3R2
Telephone: 306-668-2660
Fax: 306-975-1966
E-mail: agwest@agwest.sk.ca
Web: http://www.agwest.sk.ca
This project has been made possible with the support of the Canada-Saskatchewan Agri-Food Innovation Fund (AFIF)
Produced by: The Signature Group Inc., Saskatoon, SK