Abstract
The unintegrated circular DNA form of Moloney murine sarcoma virus (MSV) has been cloned in bacteriophage lambda. Discrete deletions in the viral genome were shown to occur during propagation of recombinant phage in Escherichia coli. Heteroduplex and restriction enzyme analyses indicated the deletion of tandemly repeated sequences within certain of the cloned MSV DNA inserts. Cloned MSV DNA was used to prepare a probe composed of its acquired cellular (src) sequences, shown previously to be necessary for MSV transformation. Analysis of EcoRI digests of normal mouse cellular DNA revealed the presence of a single 14-kilobase-pair fragment containing these sequences which lacked contiguity with endogenous type C helper viral information of the same cells. Thus, the sarcoma virus-specific sequences of MSV are represented within the normal mouse genome in a manner analogous to that of a cellular gene.