Single NOR Research Articles

Chromosome Polymorphism in Species of the Pimelodidae Family (Pisces, Siluriformes)

Cytogenetic studies of three species of the Pimelodidae family were carried out. The results showed a diploid chromosome number of 2n = 46 for Pimelodellu spl, 2n = 52 for Pimelodellu sp2 and 2n = 50 for Pinirampus pirinumpu. Chromosome polymorphism was detected by of G-banding analysis in Pimeladella spl and by C-banding in P. pirinampu. In Pimelodellu spl the 12th chromosome pair presented three G-bands on the long arm while its homologous showed only two G-bands. The 21st chromosome pair of P. pirinampu showed centromeric and interstitial heterocromatin block on one of the homologues and absence of an interstitial on other. However, the latter presented a telomeric band. In both cases the polymorphism was detected in all specimens analyzed. A deletion and an inversion rearrangement are suggested, respectively. A single NOR system was observed for three species. Considerations about the karyotype variability and evolution of the Pimelodidae family are presented.

Reliability implications in advanced embedded two-transistor-Fowler–Nordheim-NOR flash memory devices

Tail bits appearing during program/erase operation or after retention stresses are major threats to the floating-gate non-volatile memory reliability. Two-transistor (2T)-Fowler–Nordheim (FN)-NOR memories circumvent part of the tail bit induced problems of single transistor NOR and NAND configurations. However, the tail bits still represent a point of concern in the 2T-FN-NOR memory reliability, because of disturbs and stresses induced by application of the inhibition voltage and because of charge retention. In this paper the impact of tail bits in 2T-flash memory is investigated and it is suggested how to tackle this problem from design and process point of view.

Intraspecific chromosome variation between different populations ofCtenomys dorbignyi (Rodentia, Ctenomyidae) from Argentina

We used banding techniques to analyze the karyotypes of 17 individuals ofCtenomys dorbignyi Contreras and Contreras, 1984, from populations in Corrientes (Mbarigüí, the type locality, and Sarandicito) belonging to the previously known range of the species, and Entre Ríos (Tiro Federal and Paso Vera) representing a new geographically isolated group of populations. All known populations have 2n=70 although the extreme geographic isolation of the different localities suggested the possibility of chromosomal divergence. We found three different karyomorphs; two of them (Mbarigüí and Sarandicito) had 6 pairs of biarmed autosomes and 28 pairs of telocentric autosomes, with an FN=80. Pair 20 (telocentric) was the carrier of the only detected NOR. However, pair 2 was clearly different in each of these two, being metacentric in Sarandicito and submetacentric in Mbarigüí. The third fixed karyomorph differed significantly from the others, showing 8 pairs of biarmed autosomes and 26 pairs of telocentric autosomes, with an FN=84. Pair 3 (biarmed) was the carrier of the single NOR detected. The NOR carrier also showed a marked heteromorphism (Corrientes vs Entre Ríos) evidenced by differences in the length of the short arm. These observations revealed a chromosomal polytypism that was expected owing to the disjunct geographic distribution of the species.

Physical mapping of ribosomal DNA on several species of the subgenus Rosa

The localization of NORs by fluorescent in situ hybridization on metaphase spreads of five diploid (Rosa gigantea Coll., Rosa moschata Herrm., Rosa multiflora Thunb., Rosa rugosa Thunb. and Rosa sempervirens L., 2n=2x=14), one triploid (Rosa chinensis’semperflorens’ Koehne., 2n=3x=21) and one tetraploid (Rosa gallica ’versicolor’ L., 2n=4x=28) ancestral species of modern roses was studied. Two terminal hybridization signals were observed in all diploid species corresponding to a single NOR per genome in these species. Triploid R. chinensis showed three hybridization sites on the short arm of three morphologically similar chromosomes. Six hybridization sites, located at terminal positions of the short arms of three chromosome pairs, were observed in the tetraploid species. These signals corresponded to three pairs of NORs and all of them were located in chromosome pairs of different size. These observations, together with the analysis of meiotic pairing in PMCs, support the view that our specimen of R. chinensis is an autotriploid and that R. gallica’versicolor’ has an alloploidy nature.

A memory/adder model based on single C60molecular transistors

A recent proposal, in which 1-bit memory cells andsimple logic gates such as NOT and NOR gates were based onC60 molecules in an electromechanical grid acting astransistors, is extended to larger architectures. In order tomeet the requirements of standard digital circuit architectures,some modifications have to be made compared to the originalmodel. For example, the number of transistors has to be increasedfrom two to thirteen for a single NOR gate to guarantee balancedlogical levels. In the scheme employed to achieve this in thecurrent work, all two-input gates, namely OR, AND andXOR gates, can be easily constructed using the same concept.These gates are then used to design a 1-bit full-adder and aclocked D-latch, which are then combined with the earlierproposed 1-bit memory cell as the basic constituents of amemory/adder model. Clocked signal transmissions, correspondingto the read process of two 2-bit words from memory cells, theirmovement through registers and finally their addition andpassing the output through another register, are simulated usingthe electrical circuit software SPICE. For the design of thismemory/adder circuit, 464 single C60 transistors are used.

Karyotypic studies of four species of the Sorubiminae subfamily (Pisces, Siluriformes)

SUMMARYThe karyotype of the four species belonging to different genera of the Sorubiminae subfamily was analysed. In spite of some differences in chromosomal structure, all species showed the same diploid number (2n = 56) and a single NOR system which was always present in submetacentric chromosomes. C-banding pattern has been extremely conserved in this group, with heterochromatic blocks preferentially in telomeric and pericentromeric regions. In this subfamily the great karyotypic homogeneity is contrasted with the great variability of the Pimelodidae family.

Karyotype Evolution of Drymadusini (Decticinae, Orthoptera).

Karyotypes (chromosome number and shape) of eight species of the Drymadusini group were studied. The chromosome numbers in this group range from 2n_??_ = 25 to 31. Cytological analysis of these species indicate the presence of a more intensive karyotype evolution than in other genera of the Old World Decticinae. Additionally, C-band distribution and chromosomal location of the NORs were studied. Paracentromeric, interstitial, and distal C-banding in this species was observed. Three of the five analysed species showed a single active NOR located on the M2 bivalent, whereas two active NORs (primary and secondary) were observed in the two remaining species.

Chromosomal NOR Phenotypes of Seven Species of North American Cyprinidae, with Comments on Cytosystematic Relationships of the Notropis volucellus Species-Group, Opsopoeodus emiliae, and the Genus Pteronotropis

in the fifth (P. hubbsi), the single NOR was located terminally on the short arm of a large-sized acro-/subtelocentric chromosome. Pteronotropis signipinnis and P. welaka each possessed two pair of NOR-bearing chromosomes: one pair had a NOR located terminally on the short arm of a medium-sized submetacentric chromosome; whereas the other pair had a NOR located terminally on the short arm of a large-sized acro-/subtelocentric chromosome. Consideration of these and previous NOR data in North American cyprinids suggest that: 1) the N. volucellus species-group as presently constituted may not be monophyletic; 2) the species Opsopoeodus emiliae may belong in an assemblage which includes, among others, at least four species of the genus Cyprinella; 3) 0. emiliae may not be closely related to N. maculatus; and 4) P. hubbsi may belong in an assemblage which includes P. signipinnis and P. welaka, and hence may be a valid member of the genus Pteronotropis.

Localization of the nucleolar organizer and heterochromatin evolution in three European brown frogs: Rana dalmatina, Rana graeca, Rana iberica

AbstractThis study investigates the karyotypes, genome sizc, constitutive heterochromatin, and NOR localization in three European brown frog species: Rana iberica, R. dalmatina and R. graeca. The three species all possess a karyotype of 26 chromosomes. The genome size is respectively 6.9, 9.7 and 11.3 pg/N in R. iberica, R. dalmatina and R. graeca. Constitutive heterochromatin is 1.7% in R. iberica, 3.1 % in R. dalmatina and 7.0% in R. graeca. The NOR is located on the long arm of the 10th chromosome in R. iberica and R. graeca, whereas it is pericentromerically localized on the short arm of the 3rd chromosome in R. dalmatina. A single NOR extrasite is found in R. graeca. Results suggest that European brown frogs have evolved independently from North American and Asian groups. Moreover, the variation observed in constitutive heterochromatin is informative of different amplification levels of satellite-like DNA. Data also suggest that in R. dalmatina NOR localization on the 3rd chromosome may be derivcd by amplification of a pre-existing NOR site.

Silver staining in Drosophila melanogaster: NOR behaviour in heteroploid cultured cells.

A heteroploid cell line ofDrosophila melanogaster was cytologically analyzed by silver staining to investigate the in vitro behaviour of NORs. A single Ag-positive NOR was detected in all the metaphases observed, suggesting a possible suppression of excess ribosomal genes.

Dilemmas of Consensus and Division: Indonesia’s Search for a Political Format

NEITHER A SINGLE NOR A DOMINANT POLITICAL PARIY EMERGED FROM the Indonesian nationalist struggle. Rather, before the declaration of independence in August 1945, during the physical revolution against the Dutch which terminated in December 1949, and in the subsequent years the nationalist movement has been fragmented into a diversity of political groupings. Even today, after many small parties have disappeared, there remain eight legally active parties; a ninth, the PKI (Partai Komunis Indonesia), is striving to put together an underground apparatus from the ruins of 1965. As each party is the centre of a network of mass organizations, the peasants, youth, women, students and workers are also organizationally fragmented.The multiplicity of political parties is rooted in the division of Indonesian society into several distinct self-conscious, socio-cultural groupings, the alirans (lit: ‘streams’), whose distribution has changed little since 1945. They are cross-ethnic in nature and mostly encompass a broad range of socio-economic classes. The broad outlines of the aliran pattern become apparent through an examination of two fundamental cleavages that cut across society: one religious, the other between holders of traditionalist and modernist world views.