H et al).The amount of four AgNORs (two sm and two st) characterises the karyotype

H et al).The amount of four AgNORs (two sm and two st) characterises the karyotype of C.carassius (Knytl et al.b), however they varied from two to 4 as was shown in this study consistently with their transcriptional activity in the course of the preceding interphase.Intraspecific and intraindividual variation of AgNORs outcomes from that Agstaining solely detects the products of active S, .S and S rDNA expression within the preceding interphase (Reeder ).Aneta PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/21467265 Spoz et al.Comparative Cytogenetics We documented that the AgNOR internet sites were CMA good similar to what is identified in quite a few other Teleostei (Knytl et al.b).It might be interpreted as a higher copy quantity of repeating units of rDNA (Gromicho and CollaresPereira).The obtained outcomes help the hypothesis that CMA staining of GCrich heterochromatin shows all active and nonactive NORs in the chromosomes.Even so, the only four of many GCrich DNA heterochromatin sites within the karyotype of C.carassius had been linked with key ribosomal web-sites.The CMApositive web pages getting NORnegative may be associated to nucleolar dominance phenomenon reported in other organisms as well as other taxa of Teleostei, and in some hybrids and species of hybrid origin (Gromicho et al).The added CMApositive web-sites have been not discovered in C.carassius by Knytl et al.(b).The karyotype of C.carassius after DAPI staining described by Knytl et al.(b) was uniform.We gained slightly visible ATrich heterochromatic regions of DAPIcounterstained chromosomes in single LIMKi 3 custom synthesis colour FISH staining, whereas the chromosome DAPI differentiation was not revealed employing dual colour FISH.The variations may possibly outcome from the level of chromatin condensation andor technical reasons.DAPInegative staining on the NORs reported right here and described in, as an example, Rhodeus amarus (Bloch,) (Kirtiklis et al) reflected the occurrence of GCrich heterochromatin as well as the scarcity of ATrich DNA in these regions.The outcomes from FISH with S rDNA confirmed for the first time in literature that the karyotype of C.carassius (n) is characterised by the conservative number of NORs four positioned within the short arms of two sm and two st chromosomes.It was talked about by Knytl et al.(b) that this NOR chromosomal pattern supported a hypothesis on the palaeotetraploidy on the crucian carp genome as was earlier suggested by Vasil’ev and Vasil’eva .Similarly, 5 situated NORs were identified within the karyotype of a associated species C.gibelio with chromosomes (Zhu and Gui).As outlined by Foster and Bridger , the terminal position of S rDNA, regarded as a primitive stage in Teleostei, would promote chromosomal dispersion resulting from their proximity inside an interphase nucleus.The presence of a single chromosomal pair bearing S rDNA was assumed to represent an ancestral situation in fishes, considering that this pattern had been reported in species representing all so far investigated fish orders (Martins and Wasko , Nakajima et al).Taking this into consideration the presence of two pairs of NORs discovered in C.carassius may be connected with all the polyploid origin of the species.A comparable pattern with two or far more pairs of NOR chromosomes is known in species in the genus Tor (n) (Singh et al Mani et al).Nevertheless, two or several NORs have been observed in a lot of other nonpolyploid cyprinid species with n chromosomes (Pereira et al Kumar et al).The weak or missing signal of hybridisation in a single out in the 4 NORs inside the karyotype of C.carassius could be on account of either a low copy number of S rDNA or a deletion of these genes, or as a result of.