The use of cloned repetitive sequences as hybridization competitors to detect single copy sequences

To suppress background hybridization due to repetitive sequence elements, competitor Alu containing clones were isolated from a subclone library of human cosmid clone hP3.1. Pre-annealing of the probe-with this competitor increased the signal well above background. In comparison, the addition of the competitor directly to both the prehybridization and hybridization solution was more effective in reducing background. This dramatically increased the signal to noise ratio of the specific hybridization event. Application to fluorescent in situ hybridization (FISH) is readily apparent.