Characterization of cloned cDNA sequences derived from Xenopus laevis poly A(+) oocyte RNA

Double-stranded cDNA sequences were prepared from Xenopus laevis ovary poly A(+) RNA with AMV reverse transcriptase and nuclease S1. They were inserted into the plasmid pBR 322 after ligation with a Hind III linker and were cloned in E. coli strain X1776. Plasmid pools containing a cDNA insert were identified by Hind II restriction and hybridization of the DNA fragments with radiolabelled pBR 322 DNA. Hybridization of the positive pools with ovary RNA labelled in vitro led to the identification of cloned cDNA sequences which represent RNA species of high to intermediate abundance in the ovary. Positive clones were further challenged with in vitro labelled mitochondrial DNA and RNA from different developmental stages. One clone of mitochondrial origin has been detected. The hybridization characteristics of the cDNA sequences with the RNA probes from later developmental stages is discussed.