14 research outputs found
Mitotic metaphase chromosomes of <i>Triportheus trifurcatus</i> female hybridized with different labeled microsatellite-containing oligonucleotides.
<p>Chromosomes were counterstained with DAPI (blue) and microsatellite probes were directly labeled with Cy3 during synthesis (red signals). Letters mark the Z and W chromosomes. Bar = 5 µm.</p
C-banding and the repetitive DNA distribution between the Z and W chromosomes of <i>Triportheus trifurcatus</i>.
<p>Note the preferential accumulation of heterochromatin and some repeats on the W chromosomes.</p
Karyotypes of <i>Triportheus trifurcatus</i> female arranged from Giemsa-stained (above) and C-banded chromosomes (below).
<p>The ZW sex chromosomes are boxed. Note the conspicuous C-positive heterochromatin accumulated on the W chromosome. Bar = 5 µm.</p
Metaphase plates of <i>Triportheus trifurcatus</i> probed with <i>Rex1</i>, <i>Rex3</i>, <i>Rex6</i>, and telomeric (TTAGGG)<sub>n</sub> sequences.
<p>These sequences show the general distribution pattern of these repeats on the chromosomes. Letters mark the Z and W chromosomes. Bar = 5 µm.</p
Mitotic metaphase chromosomes of <i>Triportheus trifurcatus</i> male hybridized with different labeled microsatellite-containing oligonucleotides.
<p>Chromosomes were counterstained with DAPI (blue) and microsatellite probes were directly labeled with Cy3 during synthesis (red signals). Letters mark the Z chromosomes. Bar = 5 µm.</p
Repetitive DNA Sequences and Evolution of ZZ/ZW Sex Chromosomes in <i>Characidium</i> (Teleostei: Characiformes)
<div><p><i>Characidium</i> constitutes an interesting model for cytogenetic studies, since a large degree of karyotype variation has been detected in this group, like the presence/absence of sex and supernumerary chromosomes and variable distribution of repetitive sequences in different species/populations. In this study, we performed a comparative cytogenetic analysis in 13 <i>Characidium</i> species collected at different South American river basins in order to investigate the karyotype diversification in this group. Chromosome analyses involved the karyotype characterization, cytogenetic mapping of repetitive DNA sequences and cross-species chromosome painting using a W-specific probe obtained in a previous study from <i>Characidium gomesi</i>. Our results evidenced a conserved diploid chromosome number of 2n = 50, and almost all the species exhibited homeologous ZZ/ZW sex chromosomes in different stages of differentiation, except <i>C</i>. cf. <i>zebra</i>, <i>C</i>. <i>tenue</i>, <i>C</i>. <i>xavante</i> and <i>C</i>. <i>stigmosum</i>. Notably, some ZZ/ZW sex chromosomes showed 5S and/or 18S rDNA clusters, while no U2 snDNA sites could be detected in the sex chromosomes, being restricted to a single chromosome pair in almost all the analyzed species. In addition, the species <i>Characidium</i> sp. aff. <i>C</i>. <i>vidali</i> showed B chromosomes with an inter-individual variation of 1 to 4 supernumerary chromosomes per cell. Notably, these B chromosomes share sequences with the W-specific probe, providing insights about their origin. Results presented here further confirm the extensive karyotype diversity within <i>Characidium</i> in contrast with a conserved diploid chromosome number. Such chromosome differences seem to constitute a significant reproductive barrier, since several sympatric <i>Characidium</i> species had been described during the last few years and no interespecific hybrids were found.</p></div
<i>Characidium</i> species analyzed in the present study.
<p><i>Characidium</i> species analyzed in the present study.</p
Metaphase chromosome plates after FISH with CgW probe in different <i>Characidium</i> species.
<p>The sex chromosomes are indicated. Bar = 10 ÎĽm.</p
Karyotypes of <i>Characidium</i> after double-FISH with 18S rDNA probes (red), 5S rDNA (green) and snDNA U2 (in box—red).
<p>Asterisks indicate the chromosomes that harbor syntenic 5S rDNA and U2 snDNA. Bar = 10 ÎĽm.</p
Giemsa, C-banding, FISH with the 18S rDNA probe (red), 5S rDNA (green) and with CgW probe (red) of different Z and W chromosomes of <i>Characidium</i> species.
<p>Bar = 5 ÎĽm.</p