Preserving primary cDNA libraries.

A technique for the long term storage of primary cDNA libraries in a form such that relevant DNA sequences can be readily identified and retrieved is described. cDNA libraries produced using the lambda gt 10 cloning vector were plated out on host bacteria in 0.7% top agarose supplemented with 30% glycerol. Nitrocellulose lifts of these libraries were made and stored. These lifts could be screened at a later time to permit identification of bacteriophage plaques containing specific cDNA inserts. The plated libraries were then transferred to a -70 degrees C freezer. The combination of freezing and glycerol treatment allowed the bacteriophage in these primary cDNA libraries to remain viable for significantly longer than 1 year.