Hybridisation techniques on gridded high density DNA and in situ colony filters based on fluorescence detection

In our hybridisation-based approach to genome analysis (1) high density arrayed DNA and in sifu colony filters are being used to analyse large numbers of clones (2-4). So far only hazardous and radioactive labelled probes have been used successfully. However, due to their low detection resolution, densities of up to 3000 clones per 7.3 cm x 11 cm filter proved to be the limit for reliable automated image analysis. Especially in view of the expansion to arrayed cDNA libraries that contain in the order of lo5-lo6 clones each (4), an automated image analysis of much denser DNA arrays at higher resolution is required. Therefore, we have developed hybridisation procedures towards fluorescence detection techniques on nylon filters. Directly fluorescent labelled probes cannot be used so far as universal hybridisation tools on arrayed DNA filters due to a low signal to noise ratio on nylon membranes. Other non-radioactiv