title: Occurrence of 9 homologous repeat units in the external spacer region of a nuclear maize rRNA gene unit.
abstract: A 14 kb maize DNA fragment carrying nuclear rRNA genes and spacer regions was isolated and characterised by restriction enzyme mapping. A complete 3020 bp long external spacer region was sequenced and revealed 9 tandemly arranged 200 bp long repeat units with high homology. The repeat units lie upstream from two prominent S1 mapping signals. The sequence of a typical repeat unit is compared to a corresponding 130 bp long wheat repeat unit. The possible functional relevance of the repeat units is discussed.
mesh_terms: D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D004275:DNA, Ribosomal / Q000235:genetics*; D004720:Endonucleases; D012335:RNA, Ribosomal / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D015719:Single-Strand Specific DNA and RNA Endonucleases; D014908:Triticum / Q000235:genetics; D003313:Zea mays / Q000235:genetics*
chemical_list: D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D004720:Endonucleases; D004262:DNA Restriction Enzymes; D015719:Single-Strand Specific DNA and RNA Endonucleases