the 5s rdna of the bivalve cerastoderma edule nucleotide sequence of the repeat unit and chromosomal location relative to 18s–28s rdna双壳类的5 s rdna cerastoderma edule核苷酸序列的重复单元和染色体位置相对于18 s-28s rdna.pdf

Original article The 5S rDNA of the bivalve Cerastoderma edule: nucleotide sequence of the repeat unit and chromosomal location relative to 18S-28S rDNA Ana Insua Ruth Freire Josefina Méndez* Departamento de Biologia Celular y Molecular, Universidade da Coruntilde;a, A Zapateira sin, 15071 A Coruntilde;a, Spain (Received 12 February 1999; accepted 2 July 1999) Abstract - The whole 5S rDNA repeated unit of the bivalve Cerastoderma edule was amplified by PCR and several clones were sequenced. In addition, the PCR product from several individuals was digested with restriction enzymes. The results obtained indicate that 5S rDNA is organized in tandem repeats of 544-546 bp, 120 of which could represent the coding region and 424-426 the spacer region. Minimal intra- and inter-individual variation was detected, always within the spacer region. In comparison to the published 5S rRNA sequences of three other bivalves, C. edule displays a maximum of four different nucleotide positions. A specific probe of C. edule 5S rDNA was generated by PCR and used for FISH. Five chromosome pairs were identified that carried a cluster of 5S rDNA at the telomere of the long arm. After performing FISH with a heterologous 18S-28S rDNA probe and C-banding, absence of linkage between 5S and 18S-28S rDNA was demonstrated. copy; Inra/Elsevier, Paris 5S rRNA gene / non-transcribed spacer / Cerastoderma edule / FISH Résumé - L’ADNr 5S chez le bivalve Cerastoderma edule : séquence nucléotidique de l’unité de répétition et localisation chromosomique par rapport à l’ADNr 18S- 28S. L’unité de répétition complète de l’ADNr 5S a été amplifiée par PCR chez le bivalve Cerastoderma edule et plusieurs clones ont été séquencés. En outre, le produit de PCRde individus a