On spacers.
D000483:Alleles; D000818:Animals; D002466:Cell Nucleolus; D002874:Chromosome Mapping; D004261:DNA Replication; D004330:Drosophila / Q000235:genetics; D005111:Extrachromosomal Inheritance; D005796:Genes; D008040:Genetic Linkage; D008970:Molecular Weight; D012335:RNA, Ribosomal / Q000235:genetics*; D014158:Transcription, Genetic; D014981:Xenopus / Q000235:genetics
D012335:RNA, Ribosomal