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On the simplest scale, genetic engineering allows scientists to manipulate the genes within an organism. Scientists will add, subtract, and/or rearrange the DNA sequence within an organism to change it from its original form. There are three main types of genetic engineering: gene therapy, gene splicing, and cloning.

Gene therapy is used to correct faulty or defective genes. Gene splicing is used to modify plants in order to produce the best plant. Cloning is used to recreate genetic material.

All of genetic engineering has been criticized. Activists have stated that genetic engineering is allowing mankind to pick and choose what exists in regards to humans, animals, and food. They believe that this throws the balance out of the natural order of things. Dog breeders have used genetic engineering to rid some breeds of undesirable traits and boost desirable ones. The biggest argument is that mankind is now "playing God."

Proponents of genetic engineering state that it can help mankind in as multitude of ways. Defective genes in unborn babies can be manipulated or removed. Plants will grow better, stronger, and more plenteous. Animals raised for meat will have more muscle mass.

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Genetic engineering is the deliberate alteration of an organism's DNA, which stands for deoxyribonucleic acid. DNA is the substance that contains the genetic material (encoded hereditary characteristics) in living organisms. The purpose of genetic engineering is to bring about a change in the traits that an organism will pass on to its offspring.

Two genetic engineering techniques are cell fusion and recombinant DNA (also called gene-splicing or cloning). In cell fusion, the tough outer membranes (walls) of sperm and egg cells are stripped off by enzymes (digestive compounds). Then the unbounded cells are combined with the aid of chemicals or viruses. If the sperm and egg come from members of different species, the result may be the creation of a new species, or hybrid species, containing traits of both parent species.

Recombinant DNA techniques involve the splicing (uniting by overlapping or interweaving) of genes from different organisms. This is accomplished through the use of small, circular segments of DNA and a variety of enzymes. The result is the creation of hybrid DNA molecules with properties that are different from either of the parent organisms.

The process of creating recombinant DN A begins with the isolation, and fragmentation (cutting small fragments), of suitable DNA strands. These DNA fragments are carried into bacterial cells where they are spliced onto circular segments of other DNA material, called plasmid DNA. The hybrid DNA material is then mixed with other bacterial cells. Some of those cells become transformed, meaning they exhibit the desired characteristic or gene activity. The transformed cells are then separated from the other cells and grown individually in cultures.

The recombinant DNA technique has been successful in producing large quantities of hormones (such as insulin and human growth hormone) for the biotechnology industry. Despite the difficulty of transforming animal and plant cells, some genetic engineering techniques have been successful in creating disease-resistant plants and larger animals.

Because genetic engineering interferes with the processes of heredity and can alter the genetic structure of our own species, there is much concern about the ethics of genetic engineering. Questions have also been raised about the possible health and ecological consequences that may result from the creation of new forms of bacteria.

Some current applications of genetic engineering in the various fields are listed below:

  • Agriculture—Crops having larger yields; disease- and drought-resistancy; bacterial sprays to prevent crop damage from freezing temperatures; and livestock improvement through changes in animal traits.
  • Food processing—Rennin (enzyme) that prohibits the aging of cheese.
  • Industry—Use of bacteria to convert old newspaper and wood chips into sugar; oil- and toxin-absorbing bacteria for oil spill or toxic waste cleanups; and yeasts to accelerate wine fermentation.
  • Medicine—Alteration of human genes to eliminate disease (still in experimental stage); and faster and more economical production of vital human substances to alleviate deficiency and disease symptoms (but not to cure them), such as insulin, interferon (cancer therapy), vitamins, the human growth hormone ADA, antibodies, vaccines, and antibiotics.
  • Research—Modification of gene structure in medical research, especially cancer research.

Sources: Aldridge, Susan. The Thread of Life: The Story of Genes and Genetic Engineering; Cone, Robert J. How the New Technology Works, pp. 34-38; How in the World?: A Fascinating Journey Through the World of Human Ingenuity, p. 190; Oxford Illustrated Encyclopedia of Invention and ogy, pp. 153-55.

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