THE FIRST DNA PROBES for oncogenes are awaiting Food and Drug Administration approval for use in cancer diagnosis. They may become to the 1990s what cytogenetics was to the 1980s and histology to the previous decades: the best means of providing a specific diagnosis of several forms of cancer.
Although all three techniques provide a physiological indication of cellular changes related to carcinogenesis, each demonstrates something different. Histology detects gross cellular abnormalities; cytogenetics reveals alterations in banded chromosomes; molecular analysis uncovers changes in specific regions of DNA.
Molecular analysis relies on the use of DNA probes, synthetic copies of specific genes that are radioactively labeled. When these probes are added to denatured DNA samples in a procedure called Southern blotting, they will hybridize with the gene whenever it is present. Thus, they can be used to indicate a gene's chromosomal location as well as the number of times it appears