In contrast to the situation described for mammals and Drosophila, chromosome territory (CT) arrangement and somatic homologous pairing in interphase nuclei of Arabidopsis thaliana (n = 5) are predominantly random except for a more frequent association of the chromosomes bearing a homologous nucleolus organizer region. To find out whether this chromosome arrangement is also characteristic for o...

The level of redundancy of ribosomal genes, and the relationship of this level to nucleolar formation at different stages of embryonic development, have been examined in the Mexican axolotl, Ambystoma mexicanum. Individuals from 4 inbred stocks were examined, as well as descendants from 2 nucleolar variants which, in the heterozygous condition, are distinguished by exceptionally small nucleoli....

Interspecific hybrids of D. melanogaster and D. simulans normally exhibit a secondary constriction only at the D. melanogaster nucleolus organizer (NO). This phenomenon, termed nucleolar dominance, occurs only when the NO-bearing sex chromosomes of both species are present in conjunction. Experiments were initiated to localize regions on the sex chromosomes of D. melanogaster involved in mediat...

In the present study, the chromosomes numbers were confirmed, 2n = 34 for Amaranthus cruentus Linnaeus, 1759, and 2n = 32 for Amaranthus hypochondriacus Linnaeus, 1753, Amaranthus mantegazzianus Passer, 1864, and Amaranthus caudatus Linnaeus, 1753. The distribution and variability of constitutive heterochromatin were detailed using DAPI-CMA3 banding technique. The position of the nucleolus orga...

We have generated Dissociation (Ds) element insertions throughout the Arabidopsis genome as a means of random mutagenesis. Here, we present the molecular analysis of genomic sequences that flank the Ds insertions of 931 independent transposant lines. Flanking sequences from 511 lines proved to be identical or homologous to DNA or protein sequences in public databases, and disruptions within kno...

We transposed Dissociation (Ds) elements from three start loci on chromosome 5 in Arabidopsis (Nossen ecotype) by using a local transposition system. We determined partial genomic sequences flanking the Ds elements and mapped the elements' insertion sites in 1,173 transposed lines by comparison with the published genomic sequence. Most of the lines contained a single copy of the Ds element. One...

The silencing of one parental set of rRNA genes in a genetic hybrid is an epigenetic phenomenon known as nucleolar dominance. We showed previously that silencing is restricted to the nucleolus organizer regions (NORs), the loci where rRNA genes are tandemly arrayed, and does not spread to or from neighboring protein-coding genes. One hypothesis is that nucleolar dominance is the net result of h...

Activation of epidermal growth factor receptor (p-EGFR) is one of the triggers in the development of many malignant tumors, and the measurement of Argentophilic Nucleolus Organizer Regions (AgNOR) area is used as a marker of tumor proliferation. Alpha actin smooth muscle (αASM) of Original Research Article Guerra et al.; BJMMR, 13(9): 1-9, 2016; Article no.BJMMR.23933 2 peritubular cells (PT) a...

Conventional (Giemsa, C-banding, Ag - NORs) and molecular [5S rDNA, 18S rDNA, (TTAGGG)n] cytogenetic techniques were employed to study six species of the genus Eigenmannia Jordan & Evermann, 1896. They exhibited diploid chromosome numbers ranging from 2n=28 (Eigenmannia sp.1) to 2n=38 (Eigenmanniavirescens (Valenciennes, 1836)). The C-banding results revealed that species with the lowest 2n hav...

Mitotic and meiotic chromosomes of 5 species of the reptile genus Gonatodes are described by means of conventional staining, banding analyses and in situ hybridization using a synthetic telomeric DNA probe. The amount, location and fluorochrome affinities of constitutive heterochromatin, the number and positions of nucleolus organizer regions, and the patterns of telomeric DNA sequences were de...