Chromosome differentiation using nucleases: an overview

The era of the longitudinal differentiation of metaphase chromosomes (chromosome banding) dawned in 1968 when Caspersson and coworkers described the use of quinacrine mustard as a fluorescent compound which heterogeneously stained fixed human chromosomes, thus producing the so-called Q-bands. Around the same time, Pardue and Gall (1970) were experimenting with the in situ hybridization of nucleic acids to localize satellite DNAs in mouse chromosomes. Twenty five years later this technique is an indispensable tool in the approach to basic problems in various fields of Genetics and Biology. It was also in the early 1970’s that Sumner et al. (1971) and Sumner (1972) unveiled techniques of easy application to produce G- and C-bands by means of chemical pretreatment of metaphase chromosomes. The basis of chromosomal differentiation was established. Thus, the use of fluorochromes which are able to recognize GC- or AT-enriched DNA motifs, physicochemical modifications of the chromatin, and the incorporation of modern molecular techniques into cytogenetics would prove to be the first steps along new pathways in the production of longitudinal differentiation of metaphase chromosomes or interphase nuclei.