Repetitive DNA and polyploidy in selachians

Olmo, Ettore; Stingo, Vincenzo; Cobror, O.; Capriglione, Teresa; Odierna, Gaëtano

doi:10.1016/0305-0491(82)90311-x

Cited by 23 publications

(14 citation statements)

References 12 publications

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“…In this species, large amounts of highly repeated DNA [59], high heterogeneity in the genome composition [26], and a characteristic distribution of heterochromatin, that is never centromeric [36], have all been found.…”

Section: Closing Remarksmentioning

confidence: 92%

Molecular and Chromosomal Markers for Evolutionary Considerations in Torpediniformes (Chondrichthyes, Batoidea)

Rocco

2013

ISRN Genetics

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Due to their basal position in the vertebrate phylogenetic tree, the study on elasmobranch genetics and cytogenetics can provide remarkable information on the mechanisms underlying the evolution of all vertebrates. In recent years, different molecular approaches have been used to study the relationships between the different taxonomic groups of cartilaginous �sh, among them are the physical mapping of speci�c nucleotide sequences on chromosomes. However, these are controversial, particularly in Torpediniformes in which the species have different karyological parameters. e purpose of this paper is to gather the molecular markers so far present in literature that were used to reconstruct the phylogenetic position of Torpediniformes with respect to the other Batoidea and to discriminate between the various chromosome pairs in the endemic species in the Mediterranean Sea, Torpedo torpedo, T. marmorata and T. nobiliana. e 5S and 18S ribosomal DNA, the HpaI and Alu SINE, the telomeric (TTAGGG)n and the spermatogenesis-related SPATA 16, SPATA 18, and UTY sequences were particularly useful. ese last genomic segments were also able to differentiate between the male and the female karyotypes. Moreover, the torpedoes showed a particular genomic organization, especially Torpedo torpedo, in which large quantities of highly repeated DNA and a characteristic distribution of heterochromatin, which is never centromeric, were observed.

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Section: Closing Remarksmentioning

confidence: 92%

Molecular and Chromosomal Markers for Evolutionary Considerations in Torpediniformes (Chondrichthyes, Batoidea)

Rocco

2013

ISRN Genetics

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“…Although the literature now includes extensive data on genome composition in terms of DNA at varying degrees of repetitivity, information on base composition, the distribution of the heterochromatin fraction and the characterization of highly repeated DNAs (Olmo et al, 1982;Stingo, Rocco & Improta, 1989;Rocco, Stingo & Bellitti, 1996;Rocco et al, 2002a), no final conclusions can yet be made about the karyologic evolution of these vertebrates.…”

Section: Introductionmentioning

confidence: 96%

Molecular and chromosomal analysis of ribosomal cistrons in two cartilaginous fish, Taeniura lymma and Raja montagui (Chondrichthyes, Batoidea)

et al. 2005

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We used silver nitrate staining, CMA3 and FISH to study the chromosomal localization of both the major ribosomal genes and the nucleolar organizer regions as well as that of the minor ribosomal genes (5S rDNA) in two species of Batoidea, Taeniura lymma (Dasyatidae) and Raja montagui (Rajidae). In both species, all the metaphases examined showed the presence of multiple NOR-bearing sites, while the gene for 5S rRNA proved to be localized on two chromosome pairs. Furthermore, one of the two 5S rDNA sites in T. lymma was shown to be co-localized with the major ribosomal cluster. The presence of multiple nucleolar organizer regions in the two species might be interpreted as being the result of intraspecific polymorphisms, or as a phenomenon of the amplified transposition of mobile elements of the genome. We also determined the nucleotide sequence of the 5S rRNA gene, consisting of 564 bp in R. montagui and 612 bp in T. lymma. We also found TATA-like and (TGC)n trinucleotides, (CA)n dinucleotides and (GTGA)n tetranucleotides, which probably influence gene regulation.

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“…The evidence presented here confirms the particular genomic organization of elasmobranchs in heteroterms as well as in the superclass of fishes. In these species, large amounts of highly repetitive DNA [Olmo et al, 1982], high heterogeneity in the genome composition [Stingo and Rocco, 1991] and a characteristic distribution of heterochromatin [Stingo et al, 1995] were found.…”

Section: Discussionmentioning

confidence: 99%

Sex-Related Genomic Sequences in Cartilaginous Fish: An Overview

Rocco

2013

Cytogenet Genome Res

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Sex determination and differentiation are key events in the development of either the testis or ovary in fish. Sex determination mechanisms include environmental and genetic regulation. Research on sex determination systems and their related genes have been implemented in the teleost species, but the amount of information about these genes in cartilaginous fish is very scarce. This paper summarizes the few available data on molecular studies and chromosome localization of specific sequences useful to discriminate between various chromosome pairs in the common torpedo, Torpedo torpedo, and in the scyliorhinid coral catshark, Atelomycterus marmoratus, species that do not have morphologically distinct sex chromosomes. In addition, recent results obtained by sequence analysis of foxl2, a female-specific gene expressed during early phases of gonadal development in interesting key-species, such as the holocephalian Callorhinchus milii, is discussed. Nevertheless, the mechanism of sex determination in cartilaginous fish remains largely unknown. Further research needs to be carried out regarding the importance of basic and applied sex determination studies in fish, including chromosomal distribution of sex-related sequences.

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Repetitive DNA and polyploidy in selachians

Cited by 23 publications

References 12 publications

Molecular and Chromosomal Markers for Evolutionary Considerations in Torpediniformes (Chondrichthyes, Batoidea)

Molecular and Chromosomal Markers for Evolutionary Considerations in Torpediniformes (Chondrichthyes, Batoidea)

Molecular and chromosomal analysis of ribosomal cistrons in two cartilaginous fish, Taeniura lymma and Raja montagui (Chondrichthyes, Batoidea)

Sex-Related Genomic Sequences in Cartilaginous Fish: An Overview

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