Hello, normally FISH technology not require quenching but oligonucleotide probes labeled with fluorescent dyes are used in a variety of in situ applications to detect specific DNA or RNA molecules and in some cases probe fluorescence might be quenched upon hybridization in a sequence specific way.

Hi, FISH doesn't need a quencher if you just want to label and visualize the target

Hello, Jorge. FISH doesn´t need a quencher. Nevertheless, you may find better results depending on the suppliers. That is, for instance, a probe to a specific locus may show a stronger or weaker signal depending on the manufacturer.