Split Signal Fluorescence In Situ Hybridization (FISH)
The split signal FISH technique uses two differently labeled DNA-probes flanking each side of a breakpoint region. Consequently, two co-localized yellow (combined green/red) signals will be visible in normal cells, however, a chromosome translocation event will split the co-localized signal, resulting in a separate green and a separate red signal together with a yellow signal from the unaffected chromosome. To diminish background staining, the FISH probe mixture also contains unlabeled PNA blocking probes.

Sub-Deletion Signal Fluorescence In Situ Hybridization (FISH)
The sub-deletion signal FISH technique uses two differently labeled DNA-probes. One probe binds inside the deletion area while the other probe is located outside the deletion area. Consequently, two co-localized yellow (combined green/red) signals will be visible in normal cells, however, a deletion event results in the loss of one red signal from one co-localized signal, thus creating a separate green signal together with a yellow signal from the unaffected chromosome. To diminish background staining, the FISH probe mixture also contains unlabeled PNA blocking probes.