Loss of nucleolar organizer regions during chromosomal evolution in the South American cricetidGraomys griseoflavus
✍ Scribed by Andrés Zambelli; Lidia Vidal-Rioja
- Publisher
- Springer Netherlands
- Year
- 1996
- Tongue
- English
- Weight
- 404 KB
- Volume
- 98
- Category
- Article
- ISSN
- 0016-6707
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✦ Synopsis
Graomys griseoflavus is a South American phyllotine rodent having a remarkable Robertsonian polymorphism which may have produced reproductive isolation between 2n = 42-41 and 2n = 38-34 karyomorphs. Analysis of nucleolar organizer region (NOR) locations both by silver staining (Ag-NOR) and in situ hybridization revealed that 2n = 42 individuals exhibit highly variable Ag-NOR patterns, while specimens of the 2n = 38-34 karyomorphic group showed a single Ag-NOR pattern. The latter animals underwent two NOR deletions in reference to the 2n = 42 karyomorphs, one of which would be the consequence of a Robertsonian fusion and the other would be produced by the unequal crossing-over mechanism. The differential NOR homogenization supports the hypothesis that G. griseoflavus karyomorphs are evolving separately towards the acquisition of separate species status.