| "And God said...let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth." |
- Genesis 1:26 The Holy Bible
"The Earth does not belong to us. We belong to the Earth."
- Chief Seattle
Humans purposefully manipulate the evolution of other organisms. For thousands of years farmers have used selective breeding to improve their livestock and crops. As a result, we have cows that produce more milk, hens that lay more eggs, sheep with better wool, and disease-resistant plants with higher productivity. Another striking example of humans alting other organisms is the great diversity of dog breeds, from the toy poodle to the Great Dane.
Although humans have been manipulating organisms for millennia, genetic engineering simplifies and targets manipulations in an unprecedented way. Transgenic plants and animals are generated with characteristics that cannot be obtained using traditional breeding. Unlike organisms generated by selective breeding, transgenic organisms (also known as "recombinant organisms") by definition contain genes from other species. Genetic engineering techniques are used to generate recombinant DNA, which contain sequences from different organisms. This DNA then becomes incorporated into a host so that it can be passed to subsequent generations. For example, Bt corn expresses a gene for an insecticidal toxin that was "donated" by the bacterium Bacillus thuringiensis.
The use of recombinant organisms has become commonplace. For example, bacteria produce human insulin and hepatitis vaccines, and some crop plants are cultivated to be resistant to certain herbicides and insects. There are also transgenic livestock that produce human proteins, such as antithrombin III. The economic value of such products drives research. How did it start? Where is it going? What are the challenges and the risks? In this unit we will explore these questions as they relate to modifying bacteria, plants, and animals.