Sequences of 5S ribosomal RNA from Xenopus mulleri and the evolution of 5S gene-coding sequences.

Sequences for 5S RNA from somatic cells and oocytes of Xenopus mulleri are presented. Comparison with sequences previously given for Xenopus laevis indicates that the somatic 5S RNA genes of each species are more closely related to each other than either is to its own set of oocyte genes, suggesting that somatic and oocyte genes within each species are evolving independently. However, detailed analysis of sequence variants in each species suggests that there is a mechanism which allows occasional genetic exchanges between somatic and oocyte-specific genes. Possible genetic mechanisms which allows such an exchange are discussed.