"As Seen in GEN"—Flashback Volume 3, Number 4, July/Aug 1983
DNA-Based Genetic Disease Tests Tantalize But Still Elude Biomedical Researchers
By James Falkenstern
Over 1,000 diseases are now known to be transmitted via defects or mutations in the genetic material, DNA. While most inherited diseases are extremely rare in the population, approximately 30 are relatively widespread, and of substantial concern to the medical community. Genetic diseases considered to be of greatest social importance include cystic fibrosis, Huntington’s chorea, certain forms of muscular dystrophy, sickle cell anemia, hemophilia and a variety of cancers and other metabolic disorders.
Genetic diseases almost always are serious and often are incurable. Although some success in controlling these diseases has been realized through the efforts of genetic counseling services, public education, available diagnostic tests and the establishment of specialized disease programs, adequate means still do not exist to control those diseases of more widespread concern such as cystic fibrosis, Huntington’s disease, and some forms of cancer
Recent advances in recombinant DNA technology, as well as focused research efforts to characterize the genetic defects involved in the transmission of inherited diseases, promise to make earlier diagnosis and disease prevention a reality.
The technology is based on looking for genetic “markers” which are located close to the defective gene on a given chromosome. In order to make this type of testing accurate however, a significant number of family members must be tested and examined to determine the disease inheritance pattern within affected families. Eventually, scientists hope to pinpoint the exact DNA defects causing disease, and develop more specific, simpler tests.
Diagnosing and preventing genetic diseases has been severely constrained by a lack of highly specific tools to allow precise, early diagnosis of disease in fetuses, children and adults.
Biochemical and chromosomal tests vary in terms of quality and usefulness in diagnosing defects in an individual’s genetic make-up. Biochemical tests to detect female carriers of the muscular dystrophy defect have not been sufficiently reliable to use on a routine basis, and are not specific for the disease. Attempts to find a biochemical marker for carriers and patients afflicted with cystic fibrosis have also been unsuccessful thus far.
The use of karyotyping to determine genetic defects is highly accurate for determining chromosomal abnormalities in individuals and prenatal fetuses. Quantitative changes in DNA can indicate whether a child is trisomic or afflicted with Down’s syndrome. The value of the technique, however, is limited to those diseases in which a physical derangement of the chromosomal material is apparent.