The ribosomal RNA gene region in the sea urchin Lytechinus variegatus.

A fine structure map of the ribosomal gene region of the sea urchin Lytechinus variegatus has been generated. The ribosomal DNA density satellite has been analyzed with restriction enzymes and by hybridization to urchin 18S and 26S ribosomal RNA (rRNA). The L. variegatus rRNA repeats show heterogeneity on the nontranscribed spacer. Minor bands containing transcribed spacer sequences are observed. One interpretation of these bands would require both transcribed spacer heterogeneity and defective ribosomal genes retained among the rRNA gene repeats.