Application of DNA probes to hematology: an overview with selected examples

Recent advances in molecular genetics have allowed development of short segments of desoxyribonucleic acid (DNA) which are complementary to active genetic sites. By pairing normal DNA with these "molecular probes", the presence of specific genetic sequences may be detected in patient samples. The majority of hematologic diseases arise from hereditary errors, neoplastic change or parasitic organisms. These types of disorders are particularly suited to diagnosis and management using detection of abnormal DNA sequences. Sensitive laboratory techniques employing these molecular probes are now available directly to detect target DNA sequences, assess abnormal short sequences of DNA, and evaluate the presence of abnormal DNA from its transcription products. Using DNA polymerase amplification, the sensitivity of these methods approaches its theoretical limitation of a single gene pair. In hematology, a prevalent application has been the detection of clonal molecular rearrangements which serves as a marker for lymphocytic neoplasia. Other applications of these techniques include the detection of abnormal chromosomal regions such as the Philadelphia chromosome and the detection of deletions of DNA which occur in such diseases as the myeloid dysplastic syndrome. As more human genetic sequences are known, it seems likely that these techniques will become prevalent among methods of laboratory testing.