60 Instructor’s Manual for Microbiology with Diseases by Taxonomy, 5e
Pharmaceutical and Therapeutic Applications
Pharmaceutical and therapeutic applications of recombinant DNA technology include the
following:
Protein Synthesis. Scientists have inserted genes for insulin, interferon, and other proteins
into bacteria and yeast cells so that the cells synthesize these proteins in vast quantities.
“Genetically engineered” proteins are safer and less expensive than proteins isolated from
donated blood or from animals.
Vaccines. Vaccines contain the antigens of a pathogen that stimulate an immune response.
Scientists synthesize subunit vaccines—which use a portion of a pathogen rather than the
pathogen itself—by introducing genes for a pathogen’s polypeptides into vectors. When the
vectors, or the proteins they produce, are injected into a human, the body’s immune system is
exposed to and reacts against relatively harmless antigens instead of the potentially harmful
pathogen. Two variations on vaccines produced by recombinant DNA technology include
fruits or vegetables modified to produce antigenic proteins that would stimulate immunity
when consumed, and DNA vaccines, recombinant vectors that direct cells of the body to
produce the polypeptides of pathogens to develop an immune response.
Genetic Screening. Genetic mutations cause some diseases such as inherited forms of breast
cancer and Huntington’s disease. In genetic screening, laboratory technicians use DNA
microarrays to screen a patient’s blood or other tissues for these genetic mutations before the
patient shows any sign of the disease.
Gene Therapy. In gene therapy, missing or defective genes are replaced with normal genes,
with a goal of curing the genetic disease. Gene therapy can be difficult because therapeutic
levels of a functioning gene can be hard to achieve, nonetheless patients have been
successfully treated for a form of severe combined immunodeficiency disease (SCID) and a
type of blindness.
Medical Diagnosis. Clinical microbiologists now use PCR, fluorescent genetic probes, and
DNA microarrays in diagnostic applications such as examining patient specimens for
sequences unique to certain pathogens. These methods have largely replaced traditional
identification techniques.
Xenotransplants. Xenotransplants introduce animal cells, tissues, or organs into the human
body. In xenotransplants involving recombinant DNA technology, human genes are inserted
into animals to produce cells, tissues, or organs that are then introduced into the human body,
reducing the likelihood of rejection.
Biomedical Animal Models. Recombinant DNA technology can be used to modify animals
to have physiology or tissue that is “more human,” making them more useful for
understanding human disease and responses.
Agricultural Applications
Recombinant DNA technology has been applied to the realm of agriculture to produce
transgenic organisms (genetically modified organisms, GMOs), recombinant plants and
animals that have been altered for specific purposes by the addition of genes from other
organisms. Many crop plants have been made resistant to pest damage by the addition of the
gene for Bt toxin (Bt) from Bacillus thuringiensis, which kills many insect larva. Agricultural
uses of recombinant DNA technology include advances in herbicide resistance, salt tolerance,
freeze resistance, and pest and disease resistance, as well as improvements in nutritional value