The relationship between a 217-bp AluI fragment (SnAluI-33c) from lake trout (Salvelimus namaycush) which hybridizes to the nucleolar organizer regions, (NORs) and the ribosomal RNA genes was examined by Southern analysis and comparative hybridization. Restriction enzymes with recognition sites mapped in the lake trout rDNA cistron were used to digest genomic DNA into fragments of predetermined size. Comparison of the hybridization pattern of SnAluI-33c with those of two rDNA-specific probes placed this fragment within the intergenic spacer region of the rDNA cistron, approximately 3 kb upstream (5') of the 18S gene. This finding is consistent with in situ hybridization experiments showing hybridization of this fragment to sites of rDNA. Based on cross hybridization and sequence comparisons, homologous sequences are present in other salmonid species.
Bibliographical noteFunding Information:
Lake trout used in this study were obtained from D. Bast, National Fish Hatchery (Iron River, WI, USA). We thank H. McVeigh, M. Pabst, P. Rab and G. Wallace for providing DNA or tissue samples. This research was supported by grants from the NRI Competitive Grants Program/USDA (93-37205-9171) to K.M.R. and the National Science Foundation (DEB 9119293) to R.B.P.
Copyright 2007 Elsevier B.V., All rights reserved.
- Comparative hybridization
- Nucleolar organizer region