Size selection of brain cDNA library inserts. cDNA inserts obtained from tagged-random priming (RPE, lane 2), followed by Wizard column purification (lane 4), S400 MicroSpin column purification (lane 6) and agarose gel fractionation (lane 8) were analyzed by agarose gel electrophoresis. Equal amounts of DNA from each size-selection step were subjected to PCR and corresponding amplification products were analyzed (*, lanes 3, 5, 7, 9). The relevant size (bp) of the molecular weight markers (M, lanes 1, 10) are indicated on the left of the figure.