Electrically neutral backbone, a key feature of PNAs, also provides advantages in FISH (fluorescent in situ hybridization). The high specificity of PNA by electrically neutral backbone enables rapid hybridization with just a small amount of PNA probe without significant background signal, resulting in high signal-to-noise ratio and washing under mild conditions. Telomere /centromere PNA FISH probes for telomere length analysis are available with a variety of fluorescence.