Replication of injected DNA templates in Xenopus embryos

We have analysed the replication of both exogenous frog DNAs and heterologous DNAs during development from the first cleavage through the blastula stage, by their microinjection into fertilized eggs of Xenopus laevis. The data show that various plasmids increase to different extents and that the differences cannot be attributed to size alone. Plasmids containing the Xenopus ribosomal gene repeat unit do not replicate efficiently, and they also inhibit the replication of co-injected DNA templates. This inhibitory effect may be due to DNA sequences contained in the intergenic ribosomal gene spacers.