in Nanotechnology in Biology and Medicine CRC Press, 2004 For correspondence:

Microdissection as a universal tool for the generation of genetic probes Initially microdissection of genetic material was performed with extended glass-needles. This mechanical approach, in which the tip of the needle is in contact with the sample, allows the dissection of material in the range of 1 µm. The tip of an atomic force microscope (AFM) cantilever can be used to scale the dissection method down to nanometer range. Here the tip is used for manipulation and microdissection instead of imaging. The first experiments, which used extended glass-needles, were performed on polytene chromosomes of Drosophila melanogaster (Scalenghe et al., 1981). The methodical steps were transferred to mammalian and human chromosomes (Röhme et al., 1984; Fisher et al., 1985; Greenfield et al., 1987; Senger et al., 1990). The aim of these experiments was the integration of the isolated chromosomal fragments into vectors for subsequent cloning. These experiments were limited by the small amount of DNA available. This limitation was overcome by the development of polymerase chain reaction (PCR). One possibility was the introduction of primer-specific sequences, which were ligated to the microdissected DNA (Lüdecke et al., 1989; Johnson, 1990). These highly region-specific probes are extremely valuable for molecular cytogenetic studies as well as for positional cloning projects. With improvements in mechanical microdissection techniques using extended glass needles and PCR, there are two distinct methods for generating a chromosome library from microdissected chromosomal DNA: direct cloning (Fisher et al., 1985) and PCR-mediated cloning (Jung et al., 1992; Telenius et al., 1992; Stein et al., 1998). Depending on the primer, the latter metho