title: Structure of the Syrian hamster ribosomal DNA repeat and identification of homologous and nonhomologous regions shared by human and hamster ribosomal DNAs.
abstract: We have cloned and partially characterized Bam HI fragments of Syrian hamster DNA containing most of the ribosomal RNA-coding region. Several restriction site polymorphisms within the transcribed portions of the hamster rDNA repeats have been noted. Approximately three-fifths of the repeats contain a Bam HI site upstream of the 18 S coding sequences. Approximately four-fifths of the repeats contain a Bam HI site very close to the 5' end of the 28 S coding sequences. This microheterogeneity has been maintained in the DNA of baby hamster kidney (BHK)-21 cells, a cell line established nearly 20 years ago. R-loop analysis with homologous hamster rRNAs has established the size of the coding regions and the internal transcribed spacer. Heterologous R-loop analyses with cloned hamster rDNAs and human rRNAs reveal several well-defined regions within the 28 S gene where the homology between human and hamster RNAs is greatly reduced. These regions are not detectable in heteroduplexes of hamster and human rDNAs. Sequences encoding the 18 S gene do not exhibit such reduced homology.
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification; D004262:DNA Restriction Enzymes; D006801:Humans; D007668:Kidney; D008647:Mesocricetus; D008854:Microscopy, Electron; D008970:Molecular Weight; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D012335:RNA, Ribosomal / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D013045:Species Specificity; D014158:Transcription, Genetic
chemical_list: D012335:RNA, Ribosomal; D004247:DNA; D004262:DNA Restriction Enzymes