[Foreign DNA in developing embryos of the loach Misgurnus Fossilis L].

The fate of pAT153 DNA microinjected into the embryos of loach was examined. At the earliest stages of development (2 h) the high molecular weight transgenome consisting of pAT153 sequences is formed. The transgenome replicates intensively during the course of early development (until the blastula--early gastrula stages), but later the replication slows down which results in the elimination of the transgenome from the majority of embryos at more advanced stages. The analyses of the transgenome structure with the help of restriction endonucleases have shown that, after microinjection of linear DNA, the high molecular weight transgenome is formed by stochastic ligation of the sticky ends of injected molecules. Our data suggest that the transgenome formation from circular or supercoil DNA occurs after its linearization by host endonuclease.