From Genes to GMOs
Today, genes can be isolated, identified, and cloned, then inserted into other organisms to alter their traits. The process is called genetic engineering. For this technology to develop, a few tools were necessary. In the 1970s, scientists isolated bacterial plasmids. These are hulahoopshaped doublestranded units of DNA that can be moved easily from one cell to another. They also discovered "scissors," called restriction enzymes for cutting the DNA into predictable, reproducible patterns. These enzymes are used to"snip apart" plasmids at very specific DNA sequences, leaving free ends that can be rejoined as the scientist chooses. Restriction enzymes occur in bacteria as part of a natural defense mechanism to guard against invading viruses. Many different types are now available, each cutting DNA at a different sequence of base pairs.
Once a plasmid is snipped open, a foreign piece of DNA, cut by the same enzyme scissors, can be taped, end to end, into the plasmid using another enzyme, DNA ligase. This is the glue that sticks all the pieces together. The new plasmid is inserted back into a cell, where numerous copies can be made. Introduction of specific genetic material into rapidly reproducing target bacteria can turn the cells into miniature factories for production of useful substances. For example, when the Exxon Valdez oil freighter ran aground in 1989 and spilled thirtyeight million liters of oil, oileating bacteria, created in just this manner, were used in the cleanup operation. The oil was broken down five times faster with help from the genetically modified organisms (GMOs).
Plasmid technology has also been developed for moving targeted genetic material into plants. In this technique, scientists use the plasmid from a bacterium that causes tumors on plants. In nature, this bacterium transfers genetic material into plant tissues by releasing plasmids onto damaged plant cells. The plasmids enter the plant tiss
