The paper describes the construction and characterization of Lambda ZAP, a lambda insertion type cDNA cloning vector that allows in vivo excision of DNA inserts from the lambda phage. The vector incorporates the signals for both initiation and termination of DNA synthesis from the F1 bacteriophage origin of replication. This feature eliminates the need for subcloning DNA inserts into plasmids, significantly increasing the rate of clone isolation and analysis. The authors tested Lambda ZAP by preparing a chicken liver cDNA library and isolating actin clones using oligonucleotide probes. They also confirmed the ability of Lambda ZAP to serve as a vector for constructing cDNA expression libraries by detecting fusion proteins from clones containing glucocerebrosidase cDNA using rabbit IgG anti-glucocerebrosidase antibodies. The study highlights the advantages of Lambda ZAP, including its large insert capacity, unique restriction sites, and efficient in vivo excision mechanism, making it suitable for rapid DNA sequence analysis and cDNA expression.The paper describes the construction and characterization of Lambda ZAP, a lambda insertion type cDNA cloning vector that allows in vivo excision of DNA inserts from the lambda phage. The vector incorporates the signals for both initiation and termination of DNA synthesis from the F1 bacteriophage origin of replication. This feature eliminates the need for subcloning DNA inserts into plasmids, significantly increasing the rate of clone isolation and analysis. The authors tested Lambda ZAP by preparing a chicken liver cDNA library and isolating actin clones using oligonucleotide probes. They also confirmed the ability of Lambda ZAP to serve as a vector for constructing cDNA expression libraries by detecting fusion proteins from clones containing glucocerebrosidase cDNA using rabbit IgG anti-glucocerebrosidase antibodies. The study highlights the advantages of Lambda ZAP, including its large insert capacity, unique restriction sites, and efficient in vivo excision mechanism, making it suitable for rapid DNA sequence analysis and cDNA expression.