For making full lenght cdna i'm using primer extension method .plz gude me about cdna fractation process. Means which samples should i take for further construction of my library. Aftr fractanation i was not able to see my see cdna on etbr gel.however i proceed with further process and of cdna precipitation and ligation .during pptn process i saw pellet .so can anyone plz tell me which part of will give me best result n what is the basis of the column filtration provided in the kit the roche kit. Is it gel filtration ?