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Genetic Engineering
Definition
Genetic engineering involves altering the genetic structure of embryonic cells or vectors to provide them with desired traits or to eliminate undesirable traits.
Description
For thousands of years, humans have engaged in primitive forms of genetic engineering. They have chosen plants or animals with survival strength and desirable characteristics for further breeding, and have combined different strains of a species in attempts to retain and emphasize desirable characteristics of both. But in the 1970s, the field of genetic engineering took a quantum technologic leap when researchers developed a technique known as recombinant DNA, or gene splicing, enabling them to directly alter the genetic code and sequence of cells. This development transformed genetic engineering
Genes, which are composed of molecules of DNA, determine the physical characteristics that make organisms unique. Gene splicing, which involves introducing new genes into an organism in order to produce new characteristics, is performed in a number of ways. Sometimes a DNA "gun" is used to shoot genes directly into cells such as plant cells. When a gene cannot be directly "cut and pasted" from one organism to another, it may be placed in a harmless bacterium that duplicates repeatedly, acting as a "gene factory." The bacteria are then used to ferry the genes into cells.
A sheep named Dolly, born in 1997, was produced using a genetic engineering technique known as cloning. Here, scientists replaced the genetic material from one ewe's egg with genetic material from another ewe, producing an animal genetically unrelated to its surrogate mother. Hundreds of animals have been cloned, including bulls, cows, mice, monkeys, and pigs. Even clones of clones have been produced. Cloning is used to produce laboratory test animals with specific disease-related characteristics. Areas of cloning research range from cloning cows and sheep to produce medicines in their milk, to using cloning to preserve endangered species such as the Indian cheetah and the Asian guar.
Genetic engineering techniques are used to produce several widely used drugs. In addition to the hormone insulin, used to treat some forms of diabetes, these techniques are now used to produce the following: interferon, an antiviral and anticancer drug; tissue plasminogen activator (tPA), which dissolves blood clots; erythropoetin, which stimulates red blood-cell production; a hepatitis B vaccine; and others. In food production, genetic engineering can produce tomatoes with a longer shelf life; as well as crops with insect, herbicide, frost, and virus resistance. It is used to increase milk production in dairy cows, and to increase the size and infection-resistance of farmed fish like salmon. In addition, genetically altered bacteria have been used to decompose garbage and petroleum products.
Despite all its advances, the field of genetic engineering is still in its infancy. Now that researchers have mapped much of the human genome (or DNA blueprint), and some of the genes and their mutations responsible for genetic disorders like cystic fibrosis have been found, the next challenge is to understand proteins. These are the most complex of all known molecules. Each of the body's genes carries the code to create many different proteins (peptides), which are essentially the workers that carry out the DNA instructions. Understanding how messenger
proteins work is essential to preventing or curing disease. This will be a major focus of research over the next decade.
Promising areas of genetic engineering include human gene therapy and stem-cell research. Gene therapy involves repairing or replacing mutated genes in order to correct the malfunctions in protein production that can lead to disease. The use of gene therapy is being researched for diseases such as cancer, muscular dystrophy, hemophilia B, heart disease, and severe combined immune deficiency disease (known as "bubble boy disease"), among others. Stem cells are the undifferentiated cells from which specialized embryonic cells develop. They are considered one of science's best hopes for curing disease. Modified stem cells may one day be used to replace diseased cells affecting function throughout the body's systems. These cells also play an important role in tissue engineering, which involves the manufacture of blood products; artificial skin products; and biogenetic
replacement of organs, blood vessels, and cartilage. Other examples of genetic engineering research range from the manufacture of bananas engineered to contain vaccines (to eliminate the challenge of cold vaccine storage in developing countries) to coffee plants that have been altered to "switch off" caffeine before the beans even start growing.
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