Chromosome Banding and Heterochromatin in Vicia Faba

<p>This study documents the distribution of bands in Vicia faba root-tip chromosomes as shown by acid treatment, quinacrine mustard fluorescence, various forms of Giemsa banding and orcein banding methods, and demonstrates the coincidence of these bands with the position of heterochromatin as shown by cold treatment and late replication. Heterochromatin in the large metacentric M chromosome is located in two areas: (a) around the centromere and (b) adjacent to the secondary constriction. The latter is not late-replicating but is judged to represent classical nucleolus-associated heterochromatin. Heterochromatin in the smaller sub-telocentric S chromosomes is located in the intercalary and proximal areas of their long arms and in the short arm of two chromosomes. The variable expression of particular chromosome segments with different banding techniques testifies to certain differences between heterochromatic regions and emphasizes the existence of several classes of heterochromatin. In situ molecular hybridization of labelled complementary RNA to chromosomal DNA indicates the presence of repetitive DNA in both euchromatin and heterochromatin of the V. faba genome.</p>

Chromosome Banding and Heterochromatin in Vicia Faba

<p>This study documents the distribution of bands in Vicia faba root-tip chromosomes as shown by acid treatment, quinacrine mustard fluorescence, various forms of Giemsa banding and orcein banding methods, and demonstrates the coincidence of these bands with the position of heterochromatin as shown by cold treatment and late replication. Heterochromatin in the large metacentric M chromosome is located in two areas: (a) around the centromere and (b) adjacent to the secondary constriction. The latter is not late-replicating but is judged to represent classical nucleolus-associated heterochromatin. Heterochromatin in the smaller sub-telocentric S chromosomes is located in the intercalary and proximal areas of their long arms and in the short arm of two chromosomes. The variable expression of particular chromosome segments with different banding techniques testifies to certain differences between heterochromatic regions and emphasizes the existence of several classes of heterochromatin. In situ molecular hybridization of labelled complementary RNA to chromosomal DNA indicates the presence of repetitive DNA in both euchromatin and heterochromatin of the V. faba genome.</p>

Cytotaxonomy of five Arabis L. (Brassicaceae) species endemic to Turkey

In this study, the karyomorphology of five endemic Arabis taxa (A. alanyensis, A. androsacea, A. aubrietioides, A. davisii, and A. deflexa) was examined. The chromosome number of these species was determined for the first time. As a result of the karyomorphological studies, the chromosome number was determined to be x =8 for all species. Arabis androsacea and A. aubrietioides are tetraploid whereas other species are diploid. Considering the asymmetry indices, we can conclude that all taxa have symmetrical karyotypes. The most common karyotype formulas are 2n = 4x = 32m and 2n = 2x = 14m + 2sm, respectively. Arabis davisii (on the second chromosome pair) and A. deflexa (on the third chromosome pair) are distinguished from others by showing a secondary constriction.

Karyotype Analysis of the New Talpa Species Talpa aquitania (Talpidae; Insectivora) from Northern Spain

Karyotypes of 3 male Talpa specimens from northern Spain were analyzed. The mesostyles of upper molars and cytochrome b sequence analysis identified these specimens as belonging to Talpa aquitania, a new Talpa species recently described from northern Spain and southern France. We describe here for the first time the karyotype of Talpa aquitania. Its diploid number is 2n = 34 and NFa = 64, and all chromosomes including the sex chromosomes are biarmed, either metacentric or submetacentric. G-banding demonstrated that the karyotypes of T. aquitania and T. occidentalis (the most closely related species) are almost identical. However, the karyotype of T. aquitania differs from the karyotypes of both T. europaea and T. occidentalis in that it has a medium-sized biarmed Y chromosome rather than a dot-like chromosome and that chromosome 16 is submetacentric in T. aquitania but has a small p-arm in both T. europaea and T. occidentalis. Pericentromeric C-bands were scarce and only clearly visible in a few chromosomal pairs. In addition, C-banding demonstrated that half of the 14p, the 16p, and the Y chromosome are all heterochromatic. rDNA genes were located at the secondary constriction in autosomal pair 3, a common feature in the karyotypes of all Talpa species. Hybridization signals for telomeric repeats were found on the telomeres and the pericentric regions of some chromosomes and co-localized in the secondary constriction of pair 3 with the rDNA genes. In conclusion, the karyotype of T. aquitania from northern Spain is very similar to the karyotype of other species belonging to the genus Talpa.

Cytogenetic studies in three diploid species of Andropogon (Andropogoneae), section Leptopogon

Karyotypes can provide a relevant information about relationships and evolutionary origin among species of the Andropogon genus. This paper presents the karyotype, C+ and DAPI/CMA3 banding and DNA content of three diploid (2n=20) species belonging to section Leptopogon: A. selloanus, A. macrothrix and A. gyrans. Karyotypes of the three diploid species are symmetrical. We propose a karyotype formulae (18m + 2sm) for each of them. The three species show a pair of metacentric chromosomes with a terminal secondary constriction on short arms. Fluorochrome banding revealed different constitutive heterochromatin patterns and CMA3+/DAPI¬ terminal bands related to the nucleolar organizer region in each species. Nuclear DNA content was estimated by flow cytometry ranged from 2.22 to 2.61 pg. FISH technique revealed that these three species have two 45S rDNA loci at the distal ends of the short arms of two metacentric chromosomes. We compare the genomes of the diploids A. selloanus, A. macrothrix and A. gyrans, and the triploid A. ternatus using GISH. These technique allowed us to confirm the hypotheses that the A. selloanus, A. macrothrix and A. gyrans constitute a homogeneous group that share a common S genome that comprises just one of the genomes in the triploid A. ternatus.

First chromosome data on Steindachneridion doceanum (Siluriformes: Pimelodidae): a critically endangered catfish endemic of the Doce River basin, Brazil

ABSTRACT The present report represents the first cytogenetic description of Steindachneridion doceanum, great catfish which is currently at high extinction risk and it is listed as threatened on the red list of the Brazilian Ministry of the Environment, also are suggested karyotype relationships with other species of the same genus endemic from other river basins. The results revealed a diploid number of 2n = 56 and the karyotype composed of 18 metacentric, 20 submetacentric, 10 subtelocentric and 8 acrocentric chromosomes (NF = 104). The AgNORs and CMA3 signals were coincident in location occupying the short arm of an acrocentric chromosome pair (25th), in a secondary constriction. The 5S rDNA genes were localized on the short arms of one subtelocentric pair. C-banding revealed terminal blocks on the short arms on many chromosomes as well as terminal positive bands at the both ends of a submetacentric pair. C banding also revealed a large heterochromatic block in the secondary constriction (25th) region that was coincident with the AgNORs sites and CMA3+ bright bands. In spite S. doceanum represent an endemic taxon, in spite their geographic isolation their cytogenetic characteristics show similarities with other species of the genus.

NOR- bearing as a plesiomorphic characteristic in Mimus saturninus (Passeriformes Mimidae)

The order Passeriformes is the largest group of species karyotyped among birds, however little is known about the cytogenetic of the Mimidae family, registering only karyology basic data (giemsa staining). The aim of this study was to analyze the chromosomal complement from the species Mimus saturninus by conventional staining and differential chromosome banding. Diploid number and chromosome morphology were determined, as well as the distribution pattern of constitutive heterochromatin (CBG-banding), GTG-banding andAgNOR staining (NORs). The Chalk-browed Mockingbird has 2n=80. The first and fourth pairs are submetacentric and the second, third and fifth are acrocentric. The remaining chromosomes pairs of the complement have telocentric morphology. The Z chromosome is submetacentric and the W is metacentric. CBG-banding showed positive staining in the pericentromeric region of most macrochromosomes and microchromosomes and also at Z chromosome, differently from W chromosome which appeared totally heterochromatic. The GTG-banding was similar to Gallus gallus and in other species which have already been GTG-banded. The NORs were identified in a pair of microchromosomes characterized by presenting a remarkable secondary constriction. This can be considered as a plesiomorphic characteristic for M. saturninus once baseline groups (Paleognathae) also showed a pair of microchromosomes bearing NORs.

A Karyological Study in Some Species of Coffea L. and in the Closest Relative Psilanthus travancorensis (Wight & Arn.) J.-F. Leroy

Chromosome characterization were carried out in Coffea kapakata A. Chev (Bridson), C. racemosa Lour., C. salvatrix Swynn. & Philipson and in Psilanthus travancorensis (Wight & Arn.) J.-F. Leroy (2n=22) by employing the conventional acetic orcein technique as well as by C- and NOR-banding aiming further comparative studies. Although C. canephora and C. dewevrei have already been studied and depict a C-band karyotype, they have also been included for further comparisons, since NOR-banding and some other morphometric data have not been obtained yet. However, there were observed some differences among the species regarding chromosomal morphometry. The karyotype formula obtained was 3m+6sm+2sms for C. salvatrix and P. travancorensis, 1M +2m + 6sm + 2sms for C. kapakata and 2M +1m + 6sm + 2sms for C. racemosa. All species displayed a moderate karyotype asymmetry and according to Stebbins system, C. canephora, C. dewevrei, C. kapakata and C. racemosa were classified as 3B while C. salvatrix and P. travancorensis were classified as 2A. Among the four indices used to assess karyotype asymmetry, Paszko AI index along with Stebbins were best suited to individualize the species. C-bands were preferentially situated at a pericentromeric/centromeric position. Two pairs of chromosomes, with secondary constriction and satellite segments, were observed in all the species following acetic orcein staining. C. racemosa and C. salvatrix showed NOR-band in both pairs, while only one chromosome pair carrying NOR-band was seen in C. canephora, C. dewevrei, C. kapakata and P. travancorensis. Data on chromosome morphometry, asymmetry indices and NOR-banding were suitable for the characterization of the species.

Cytogenetic description of Bunocephalus doriae Boulenger, 1902 (Siluriformes: Aspredinidae) from the Paraná River (Misiones, Argentina)

In this work, Bunocephalus doriae was cytogenetically analyzed. A karyotype with a diploid number of 2n= 50 comprising 6m, 10sm, 6st, and 28a (FN= 72) chromosomes was observed. The occurrence of an asymmetric karyotype with a large number of acrocentric chromosomes distinguishes this species from others the Order Siluriformes. An exclusive character observed is the first pair of subtelocentric as the largest chromosome pair of the complement. NORs detected using AgNO3 were located in the terminal regions, on the short arm of a subtelocentric chromosome pair (pair 11), in a secondary constriction. C-banding revealed heterochromatic centromeric regions on several chromosomes of the complement after C-banding. This is the first cytogenetic description of this species and the first cytogenetic report on a member of the family Aspredinidae.