Cytogenetic characterization and mapping of rDNAs,core histone genes and telomeric sequences in <Emphasis Type="Italic">Venerupis aurea</Emphasis> and <Emphasis Type="Italic">Tapes rhomboides</Emphasis> (Bivalvia: Veneridae) |
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Authors: | Joana Carrilho Concepción Pérez-García Alexandra Leitão Isabel Malheiro Juan J Pasantes |
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Institution: | 1.Department of Biochemistry, Genetics and Immunology,University of Vigo,Vigo,Spain;2.Cytogenetics Laboratory, Instituto de Ciências Biomédicas Abel Salazar,University of Porto,Porto,Portugal;3.Centro de Estudos de Ciências Animais (CECA/ICETA),University of Porto,Porto,Portugal;4.Instituto Nacional de Recursos Biológicos (INRB/L-IPIMAR),Olh?o,Portugal |
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Abstract: | We describe the chromosomal location of GC-rich regions, 28S and 5S rDNA, core histone genes, and telomeric sequences in the
veneroid bivalve species Venerupis aurea and Tapes (Venerupis) rhomboides, using fluorochrome staining with propidium iodide, DAPI and chromomycin A3 (CMA) and fluorescent in situ hybridization (FISH).
DAPI dull/CMA bright bands were coincident with the chromosomal location of 28S rDNA in both species. The major rDNA was interstitially
clustered at a single locus on the short arms of the metacentric chromosome pair 5 in V. aurea, whereas in T. rhomboides it was subtelomerically clustered on the long arms of the subtelocentric chromosome pair 17. 5S rDNA also was a single subtelomeric
cluster on the long arms of subtelocentric pair 17 in V. aurea and on the short arms of the metacentric pair 9 in T. rhomboides. Furthermore, V. aurea showed four telomeric histone gene clusters on three metacentric pairs, at both ends of chromosome 2 and on the long arms
of chromosomes 3 and 8, whereas histone genes in T. rhomboides clustered interstitially on the long arms of the metacentric pair 5 and proximally on the long arms of the subtelocentric
pair 12. Double and triple FISH experiments demonstrated that rDNA and H3 histone genes localized on different chromosome
pairs in the two clam species. Telomeric signals were found at both ends of every single chromosome in both species. Chromosomal
location of these three gene families in two species of Veneridae provides a clue to karyotype evolution in this commercially
important bivalve family. |
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