Inactive ribosomal cistrons are spread throughout the B chromosomes of Rattus rattus (Rodentia, Muridae). Implications for their origin and evolution

In-situ hybridization with a rDNA probe has demonstrated the presence of non-transcribed ribosomal genes in the B chromosomes of the black rat Rattus rattus. To test whether methylation of ribosomal DNA present in the B chromosomes could account for their inactivation, we performed in-situ digestion...

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Bibliographic Details
Published in:Chromosome research 2000-01, Vol.8 (4), p.305-311
Main Authors: Stitou, S, Díaz de La Guardia, R, Jiménez, R, Burgos, M
Format: Article
Language:English
Subjects:
Animals
Blotting, Southern
Chromosome Banding
Chromosomes - ultrastructure
Deoxyribonuclease HpaII - metabolism
Deoxyribonucleic acid
DNA
DNA Methylation
DNA, Ribosomal - metabolism
DNA-Cytosine Methylases - metabolism
Evolution, Molecular
Female
Heterochromatin - ultrastructure
In Situ Hybridization
Karyotyping
Male
Microbiology
Muridae
Rats - classification
Rats - genetics
Rattus rattus
Repetitive Sequences, Nucleic Acid
Ribosomes - ultrastructure
Rodentia
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Summary:In-situ hybridization with a rDNA probe has demonstrated the presence of non-transcribed ribosomal genes in the B chromosomes of the black rat Rattus rattus. To test whether methylation of ribosomal DNA present in the B chromosomes could account for their inactivation, we performed in-situ digestions and Southern analyses of DNA digested with the isoschizomers MspI and HpaII. Our results suggest that the accessory chromosomes of this species have originated from one of the smaller NOR-carrying chromosome pairs. In the course of evolution, repetitive sequences invaded this supernumerary element and its ribosomal DNA content was dispersed throughout the chromosome and inactivated by heterochromatinization and methylation.
ISSN:0967-3849
1573-6849
DOI:10.1023/A:1009227427575