Normalized nucleic acid libraries and methods of production thereof

The present invention relates generally to methods for producing normalized nucleic acid libraries in which each member of the library can be isolated with approximately equivalent probability. In particular, the present methods comprise subtractive hybridization of a nucleic acid library with haptenylated (e.g., biotinylated, avidinated or streptavidinated) nucleic acid molecules that are complementary to one or more of the nucleic acid molecules of the library, such that the variation in the abundances of the individual nucleic acid molecules in the library is reduced. The invention also relates to production of normalized nucleic acid libraries (particularly cDNA libraries) in which contaminating nucleic acid molecules have been reduced or eliminated, and to normalized nucleic acid libraries produced by such methods.