Direct Cloning of Agtll cDNA Inserts Into a Plasmid Vector

Cloning vectors derived from bacteriophage λ are used frequently in the construction of both cDNA and genomic DNA libraries (1 ). The screening of positive plaques from λ libraries is relatively easy with the plaque lifting technique of Benton and Davis (2 ). However, isolating and subcloning recombinant inserts from the phage clones of interest can be a tedious task. Additionally, if the insert comprises more than one restriction fragment, the smaller fragments may be missed during the subcloning steps. Both polymerase chain reaction (PCR) (3 ,4 ) and plasmid rescue using the f 1 origin of replication, as in the λZAP systems (5 ), were developed to circumvent this problem. However, these sophisticated procedures may not exist in every molecular cloning laboratory and most of the existing cDNA libraries are constructed in λgt vectors. Here we describe a direct method of cloning inserts from λgt phage into a pBR322 cloning vector.