Quality control of cDNA and sub-libraries Panel A: Amplified cDNA size fractions. cDNA was size-fractionated and separate size fractions (1–4) were PCR-amplified. U = unfractionated control, size marker in kb. Panel B: Insert analysis of sub-libraries obtained by cloning of the amplified size fractions shown in panel A. Plasmid DNA of clone pools of 5,000–10,000 clones was restriction digested by Sfi I. An arrow head indicates the vector band. The smear corresponds to the insert size range of the the sub-library.