title: Amplified ribosomal spacer sequence: structure and evolutionary origin.
abstract: A novel class of repeated sequences consisting of tandem arrays of ribosomal spacer sequence has been discovered in a mouse genome. Comparison to normal ribosomal DNA reveals that one repeat unit consists of two separate parts of spacer sequence. This amplified spacer sequence has a pseudogene-like structure but is distinct from the previously reported pseudogenes and orphons in regions lacking coding sequences. So far the amplified spacer sequence has been found only in the BALB/c mouse genome but not in ten other laboratory strains and several wild-type mouse stocks. Surprisingly, a part of the amplified spacer sequence unit had a higher homology to the corresponding part of the ribosomal DNA sequence of Mus musculus molossinus, a Japanese wild-type mouse, than to the corresponding part of the rDNA of the BALB/c mouse. These findings suggest that the amplified spacer sequence of the BALB/c mouse might have partly originated in M. m. molossinus or in a related subspecies.
authors.forename: R
authors.initials: R
authors.lastname: Kominami
authors.forename: M
authors.initials: M
authors.lastname: Muramatsu
mesh_terms: D000818:Animals; D001483:Base Sequence; D004274:DNA, Recombinant; D004275:DNA, Ribosomal; D051379:Mice; D008807:Mice, Inbred BALB C; D009693:Nucleic Acid Hybridization; D012335:RNA, Ribosomal
chemical_list: D004274:DNA, Recombinant; D004275:DNA, Ribosomal; D012335:RNA, Ribosomal