Unique sequence DNA transcripts present in mature oocytes of Urechis caupo.

DNA - DNA reannealing of sheared Urechis caupo DNA indicates that the genome is composed of two major repetitive sequence families. The repetitive sequence DNA families compose 8 and 7% of the DNA and are repeated in the genome on an average of 2.0 - 10-6 and 6.0 - 10-3 times, respectively. The unique sequence DNA composed a minimum of 75% of the genome and the rate of reannealing indicates a complexity of 2.6 - 10-8 nucleotide pairs per genome. Hybridization of isolated 3-H-labeled unique sequence DNA with an excess of unlabeled mature oocyte RNA provides a minimum estimate of the genetic diversity of the RNA present in the mature oocytes. The apparent saturation level of unique sequence DNA with RNA indicates that about 8.6% of the unique sequence DNA is expressed. Based on the fraction of the DNA that forms a stable hybrid and the complexity of the unique sequence DNA the RNA present in the mature oocyte is a complementary with 2.2 - 10-7 nucleotide pairs of unique sequence DNA.