What is a transgenic animal/plant?
A transgenic animal or plant is one that has a foreign gene (called a "transgene") inserted into its DNA. Transgenic animals and plants are sometimes called "genetically modified organisms" or GMO's for short.
What is a transgene?
A transgene is the foreign gene that has been moved from one organism into a new organism by genetic engineering. For example, a bacterial gene that is inserted into a plant's DNA would be a transgene.
What is the difference between traditional plant and animal breeding and transgenic technology?
In traditional plant or animal breeding, a plant or animal with a desired trait is mated with an existing plant or animal, to transfer the desired trait to the offspring. Of course, the only genes that are involved are the genes already present in the parental plants or animals. For example, if you mate rabbits, the only genes that you can expect to find in the baby rabbits are rabbit genes, which came from a rabbit egg and a rabbit sperm.
In transgenic technology, by contrast, a single gene from one organism, say a camel, could be inserted (by injection) into fertilized rabbit eggs. The camel gene would insert itself into the rabbit's DNA in some of the eggs (the success rate of this is fairly low). The rabbit eggs would then be returned to a female rabbit's womb, where the baby rabbits would develop. The eggs where a camel gene is inserted will divide and pass on the camel gene into all the cells of the developing baby rabbit, so that when it is born all of its cells now have a camel gene in them. As you can imagine, there is no "natural" way that a rabbit would mate with a camel and end up with camel genes, but with transgenic technology this is made possible. Transferring genes across species by this technology has made it possible to put human genes into goats, bacterial genes into plants and jellyfish genes into frogs.
Why would anyone want to do such bizarre things?
There are many reasons that people want to transfer genes from one species to another.
One reason is to make pest-resistant plants. Certain bacteria produce a toxic substance that can kill insect pests that feed on crop plants. If we insert the gene for this toxin into the DNA of crop plants, then the plants would produce the toxin and any insects that attacked the plants would be killed. In this way, the plant would be able to ward off insect pests.
Another reason for putting the genes of one species into another species is to make life saving drugs in large amounts. If we insert the gene for, say, insulin, or blood-clotting factors into cows, in the right way, then we can get the cows to produce the insulin or clotting factors in their milk. Since a single dairy cow can produce up to 10,000 quarts of milk in a year, this would assure a plentiful and cheap supply of these therapeutic compounds. Remember that insulin and the clotting factors are made by humans, and we can't really use human beings as a source for these compounds, certainly not to produce the quantities that are needed.
The general principle of producing a GMO is to add a lot of genetic material into an organism's genome to generate new traits - Genetic engineering - was made possible through a series of scientific advances including the discovery of DNA and the creation of the first recombinant bacteria in 1973, i.e., E .coli expressing a salmonella gene. This led to concerns in the scientific community about potential risks from genetic engineering which have been thoroughly discussed at the Asilomar Conference in Pacific Grove, California. The recommendations laid out from this meeting were that government oversight of recombinant DNA research should be established until the technology was deemed safe. Herbert Boyer then founded the first company to use recombinant DNA technology, Genentech, and in 1978 the company announced the creation of an E....