Persistence and integration of cloned DNA in postembryonic sea urchins.

Cloned DNA was injected into the cytoplasm of unfertilized sea urchin eggs which were then fertilized and cultured in the laboratory through metamorphosis. The exogenous DNA replicated manyfold and persisted for weeks in a majority of growing larvae, as shown by hydridizing "dot blots" of the DNA of single individuals with appropriate labeled probes. After metamorphosis 5-15% of the juvenile sea urchins retained the exogenous sequences. Genomic integration of the exogenous sequence was observed in the DNA of a postmetamorphosis juvenile.