Since its introduction, fluorescence in situ hybridiza­tion (FISH) has found multiple uses in molecular research and diagnosis, due to its unique capability of visualizing nucleic acid sequences without altering the cell’s cytologi­cal and chromosomal integrity. The improvement of the FISH technique has led to the development of new meth­odologies for chromosomal screening in both metaphases and interphasic nuclei, and consequently the FISH tech­nique has rapidly found increasing applications in cyto­genetics. However, for the identification of human chro­mosomes, the FISH procedure can be hampered by the lack of specificity of some centromeric probes and the occurrence of artefactual binding sites [1,2].

In recent years, alternative methods to FISH have been introduced, and have shown to be valuable in detecting chromosomes and quantifying aneuploidies. These alterna­tive procedures are the primed in situ (PRINS) labeling and the peptide nucleic acid (PNA) probes. This paper provides a brief overview of both PRINS and PNA tech­niques. Some of the latest innovative improvements of these techniques and their practical applications are pre­sented.