title: The ribosomal DNA transcription unit of the house cricket, Acheta domesticus.
abstract: A composite map representing a single ribosomal DNA repeat unit of the house cricket, Acheta domesticus, was constructed from overlapping cloned fragments. Sites in the repeat unit for nine restriction enzymes were mapped. R-loop mapping of sequences coding for 18 S and 28 S RNA demonstrates that the 58-kb ribosomal DNA repeat unit contains a novel-sized internal transcribed spacer of 8.4 kb. The existence of this large spacer was confirmed in genomic DNA, most if not all of the genomic repeat units containing such a spacer. A 15- to 17-kb ribosomal RNA precursor transcript is synthesized as predicted on the basis of the size of the internal transcribed spacer. The 5.8 S RNA gene is localized to a 1-kb sequence immediately 5' to the 28 S gene. The coding regions examined contain no intervening sequences analogous to those described within ribosomal DNA of other eukaryotes. Only 11% of the repeat unit codes for mature ribosomal RNA, while the remainder is nontranscribed (71%) and transcribed (18%) spacer DNA.
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D004275:DNA, Ribosomal / Q000235:genetics*; D005796:Genes; D006135:Gryllidae / Q000235:genetics*; D009693:Nucleic Acid Hybridization; D009987:Orthoptera / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D004275:DNA, Ribosomal; D012335:RNA, Ribosomal