ABSTRACT
In situ hybridization of nucleic acids to chromosomes has become a widely used method of gene mapping in a variety of species. Chromosomal sites that have annealed with the probes are identified via differential staining of each chromosome. Localization of genes to sites involved in chromosome translocations may aid in revealing the environmental mutagenic events leading to the formation of fusion genes involved in cancer. Chromosomes exhibit a reproducible structural pattern when obtained from prophase, prometaphase, and metaphase cells. In order to prepare chromosomes from tissues with low mitotic activity, long-term cell and tissue culture is often employed. Slides containing metaphase chromosomes are incubated in a ribonuclease solution to destroy RNA and prevent probe hybridization to nuclease nonchromosomal nucleic acids. Chromosome banding techniques for in situ hybridization fall into two main categories, prebanding and postbanding. Metaphase chromosomes are viewed under the light microscope after the slides have been stained in a buffered Giemsa solution.
