I am currently trying to perform fluorescence in situ hybridization on metaphase spreads using a split probe. When I visualize the slides, the chromosomes are clearly stained with DAPI, but I cannot see the probe on the chromosomes at all. I use a formamide/SSC solution to denature the DNA and I denature the probe at 75C for 5 minutes. I wash the slides in igepal/SSC heated to 73C then room temperature igepal/SSC. Is there a place in my protocol where an error may be occurring?