|Google search image: Transgenic Animal. Human ear on mouse.|
The term transgenic animal refers
to an animal in which there has been a deliberate modification of the
genome - the material responsible for inherited characteristics - in contrast
to spontaneous mutation . Foreign DNA is introduced into the animal, using
recombinant DNA technology, and then must be transmitted through so that
every cells, of the animal contain the same
Transgenic Animals as Biotechnology
Transgenic animals are just one in a series of developments in the area of biotechnology. Biotechnology has transformed the way in which we understand processes such as engineering and manufacturing. These terms now include the use of living organisms or their parts to make or modify products, to change the characteristics of plants or animals, or to develop micro-organisms for specific uses. . Genetic manipulations at the level of DNA have also changed long held views as to what is considered to be animal, plant and human.
Consideration of the acceptability of creating specific transgenic animal strains or genetic manipulation involving interchanging DNA between species and kingdoms could be a simple animal care issue or a societal decision. The following is an attempt to show what the ability to create transgenic animals or engage in other forms of DNA manipulation means in terms of traditional ACC functions, not forgetting that this impacts on wider considerations of human responsibility for the welfare of other life forms.The creation of transgenic animals is resulting in a shift from the use of higher order species to lower order species.
1. Historical background
Prior to the development of molecular genetics, the only way of studying the regulation and function of mammalian genes was through the observation of inherited characteristics or spontaneous mutations. Long before Mendel and any molecular genetic knowledge, selective breeding was a common practice among farmers for the enhancement of chosen traits.
The mutual contributions of developmental biology and genetic engineering permitted rapid development of the techniques for the creation of transgenic animals. DNA microinjection, the first technique to prove successful in mammals, was first applied to mice (Gordon and Ruddle, 1981) and then to various other species such as rats, rabbits, sheep, pigs, birds, and fish. Two other main techniques were then developed: those of retrovirus-mediated transgenesis (Jaenisch, 1976) and embryonic stem (ES) cell-mediated gene transfer (Gossler et al., 1986).
Since 1981, when the term transgenic was first used by J.W. Gordon and F.H. Ruddle (1981), there has been rapid development in the use of genetically engineered animals as investigators have found an increasing number of applications for the technology.
Marie Buy, Editorial Assistant, Canadian Council on Animal Care (CCAC)
(From CCAC Resource Supplement, Spring/Summer 1997.