LONG HISTORY
The animal biotechnology in use today is built on a long history. Some of the first biotechnology in use includes traditional breeding techniques that date back to 5000 B.C.E. Such techniques include crossing diverse strains of animals (known as hybridizing) to produce greater genetic variety. The offspring from these crosses then are bred selectively to produce the greatest number of desirable traits. For example, female horses have been bred with male donkeys to produce mules, and male horses have been bred with female donkeys to produce hinnies, for use as work animals, for the past 3,000 years. This method continues to be used today.
The modern era of biotechnology began in 1953, when American biochemist James Watson and British biophysicist Francis Crick presented their double-helix model of DNA. That was followed by Swiss microbiologist Werner Arber’s discovery in the 1960s of special enzymes, called restriction enzymes, in bacteria. These enzymes cut the DNA strands of any organism at precise points. In 1973, American geneticist Stanley Cohen and American biochemist Herbert Boyer removed a specific gene from one bacterium and inserted it into another using restriction enzymes. That event marked the beginning of recombinant DNA technology, or genetic engineering. In 1977, genes from other organisms were transferred to bacteria, an achievement that led eventually to the first transfer of a human gene.
THE TECHNOLOGY INVOLVED
Animal biotechnology in use today is based on the science of genetic engineering. Under the umbrella of genetic engineering exist other technologies, such as transgenics and cloning, that also are used in animal biotechnology.
Transgenics
Transgenics (also known as recombinant DNA) is the transferal of a specific gene from one organism to another. Gene splicing is used to introduce one or more genes of an organism into a second organism. A transgenic animal is created once the second organism incorporates the new DNA into its own genetic material.
In gene splicing, DNA cannot be transferred directly from its original organism, the donor, to the recipient organism, or the host. Instead, the donor DNA must be cut and pasted, or recombined, into a compatible fragment of DNA from a vector — an organism that can carry the donor DNA into the host. The host organism often is a rapidly multiplying microorganism such as a harmless bacterium, which serves as a factory where the recombined DNA can be duplicated in large quantities. The subsequently produced protein then can be removed from the host and used as a genetically engineered product in humans, other animals, plants, bacteria or viruses. The donor DNA can be introduced directly into an organism by techniques such as injection through the cell walls of plants or into the fertilized egg of an animal.
This transferring of genes alters the characteristics of the organism by changing its protein makeup. Proteins, including enzymes and hormones, perform many vital functions in organisms. Individual genes direct an animal’s characteristics through the production of proteins.