Recombinant DNA technology has been used for many purposes. The Human Genome Project has relied on recombinant DNA technology to generate libraries of genomic DNA molecules. Proteins for the treatment or diagnosis of disease have been produced using recombinant DNA techniques. In recent years, a number of crops have been modified using these methods as well.

As of 2001, over eighty products that are currently used for treatment of disease or for vaccination had been produced using recombinant DNA techniques. The first was human insulin, which was produced in 1978. Other protein therapies that have been produced using recombinant DNA technology include hepatitis B vaccine, human growth hormone, clotting factors for treating hemophilia, and many other drugs. At least 350 additional recombinant-based drugs are currently being tested for safety and efficacy. In addition, a number of diagnostic tests for diseases, including tests for hepatitis and AIDS, have been produced with recombinant DNA technology.

Gene therapy is another area of applied genetics that requires recombinant DNA techniques. In this case, the recombinant DNA molecules themselves are used for therapy. Gene therapy is being developed or attempted for a number of inherited human diseases.

Recombinant DNA technology has also been used to produce genetically modified foods. These include tomatoes that can be vine-ripened before shipping and rice with improved nutritional qualities. Genetically modified foods have generated controversy, and there is an ongoing debate in some communities about the benefits and risks of developing crops using recombinant DNA technology.

Since the mid-1970s, recombinant DNA techniques have been widely applied in research laboratories and in pharmaceutical and agricultural companies. It is likely that this relatively new area of genetics will continue to play an increasingly important part in biological research into the foreseeable future. see also Biotechnology; Cloning Genes; Crossing Over; DNA Libraries; Escherichia coli; Gene Therapy: Ethical Issues; Genetically Modified Foods; Human Genome Project; Plasmid; Restriction Enzymes; Reverse Transcriptase; Transposable Genetic Elements.

Patrick G. Guilfoile


Cooper, Geoffrey. The Cell: A Molecular Approach. Washington, DC: ASM Press, 1997.

Glick, Bernard, and Jack Pasternak. Molecular Biotechnology: Principles and Applications of Recombinant DNA, 2nd ed. Washington, DC: ASM Press, 1998.

Kreuzer, Helen, and Adrianne Massey. Recombinant DNA and Biotechnology, 2nd ed. Washington, DC: ASM Press, 2000.

Lodish, Harvey, et al. Molecular Cell Biology, 4th ed. New York: W. H. Freeman, 2000.

Old, R. W., and S. B. Primrose. Principles of Gene Manipulation, 5th ed. London: Blackwell Scientific Publications, 1994.

Internet Resource

"Approved Biotechnology Drugs." Biotechnology Industry Organization. <http://>.

Repetitive DNA Elements

The human genome contains approximately three billion base pairs of DNA. Within this there are between 30,000 and 70,000 genes, which together add up to less than 5 percent of the entire genome. Most of the rest is made up of several types of noncoding repeated elements.

Most gene sequences are unique, found only once in the genome. In contrast, repetitive DNA elements are found in multiple copies, in some cases thousands of copies, as shown in Table 1. Unlike genes, most repetitive elements do not code for protein or RNA. Repetitive elements have been found in most other eukaryotic genomes that have been analyzed. What functions they serve, if any, are mainly unknown. Their presence and spread causes several inherited diseases, and they have been linked to major events in evolution.

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