Comparison of the nuclear ribosomal units of five Chlamydomonas species

The organization of the nuclear ribosomal units of five different species of Chlamydomonas has been examined by hybridization of their nuclear DNA fragments produced by several restriction endonucleases with a radioactively labelled probe consisting of the two cloned BamHI ribosomal fragments of C. reinhardii. The results indicate that a) the ribosomal units of these five species are structurally related, b) changes in the non transcribed spacer occur in C. eugametos and in C. globosa, c) the rDNA unit of C. intermedia contains either an enlarged internal transcribed spacer or a ribosomal intervening sequence, d) the rDNA units of C. reinhardii and C. callosa are indistinguishable.