The technique employs probes with a base sequence complementary to that of the sought target nucleic acid. In this discussion, we will focus on cytogenetic analysis and gene expression. The cytogenetic evaluation of human neoplasms has been most actively pursued in hematologic tumors. Highly useful diagnostic and prognostic information that is complementary to conventional morphologic and immunologic assessment of a neoplasm is afforded by cytogenetic analysis. This said, the method requires living cells capable of dividing, a high level of technical and interpretive expertise, and is costly.
Many probes are now commercially available.
Because the centromeres of human chromosomes are characterized by unique highly repetitive DNA sequences, they can be detected by large heavily labeled probes that hybridize to a specific chromosome. These markers are particularly useful for identification of numerical abnormalities. Paint probes consist of a cocktail of many genomic sequences from a chromosome specific library. They are particularly useful in analyzing complex chromosomal rearrangements in metaphase preparations. They have limited utility in the analysis of interphase cells because their signals are large and not well localized.