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. © Inra/Elsevier, Paris
Highlights
The 5S ribosomal DNAs (5S rDNA) of many eukaryotes has been cloned and characterized
The inferred coding region of the C. edule 5S rDNA is invariable between clones, ignoring the sequence corresponding to primer A in clones Cel and Ce2
This is the first report on the characterization of the whole 5S rDNA repeat unit in a bivalve species
Summary
The 5S ribosomal DNAs (5S rDNA) of many eukaryotes has been cloned and characterized. In most cases, it is organized as clusters of tandem repeats of several hundred base pairs (bp), consisting of a coding region and a nontranscribed spacer region !14!. Accumulated data demonstrate that, while the coding region is highly conserved among taxa, both with respect to length and nucleotide sequence, the spacer region evolves more rapidly and can show variation both within and between species Xenopus laevis has three types of 5S rDNA sequences with developmentally regulated expression !32]. More than one type of 5S rDNA sequence with differential expression was seen in the chicken [13] and some fish [12]. 5S rDNA sequences are regarded as potentially useful in revealing phylogenetic relationships
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call