Plasmid and bacteriophage λ-DNA show differential replication characteristics following injection into fertilized eggs of Xenopus laevis: Dependence on period and site of injection

The fate of DNA injected into in vitro fertilized eggs of Xenopus laevis during subsequent early embryogenesis was investigated by changing the time period and the area of injection. Form $\text{I}\text{II}$ plasmid DNA was found to be preferentially replicated in embryos which had been injected 60–65 min after fertilization into the animal half of the fertilized egg, irrespective of the presence of a eukaryotic origin of replication sequence element in the DNA probe used for injection. In the experiments where plasmid DNA and λ-DNA were coinjected, only the latter was actively replicated, which suggests an inhibitory activity of this DNA on replication of coinjected plasmid DNA.