1979 Researchers develop a shortcut to Southern blotting. Instead of separating DNA by size, biologists simply plop mixtures of DNA onto filter paper in big dots. These "dot blots," like their Southern cousins, are then probed for matches with radioactively labeled DNA fragments. (Dot blots that contain DNA samples taken from different organisms are affectionately dubbed "zoo blots.") DNA chips are essentially dot blots in which samples are spotted onto glass slides rather than filter paper.