In the non-normalized library, high and medium abundance genes have a greater chance of being sequenced than rare transcripts. This approach may be useful for initial gene discovery using pooled samples of several different tissues, when little is known about an organism. 

Direct random sequencing of clones from standard cDNA libraries is inefficient for discovering rare transcripts, because cDNA of medium and high abundance are sequenced repeatedly instead. Normalization performed before cDNA library sequencing decreases the prevalence of clones representing abundant transcripts. Thus, our normalization increases the efficiency of random sequencing dramatically, and is essential for rare gene discovery.More information, please visit the website: http://www.cd-genomics.com/Non-Normalized-cDNA-library-construction-service.html