Search results for "CHROMOSOME"
showing 10 items of 1175 documents
Patterns of puffing activity and chromosomal polymorphism in Drosophila subobscura II. Puffing patterns at the prepupa stage
1985
Puffing activity patterns of the five large polytene chromosomes of Drosophila subobscura were studied during the late third-larval instar and through the prepupal period. A total of 166 loci active in some of the eleven stages studied were described. The distribution of these active loci per chromosome is the following: 25 on chromosome A, 33 on chromosome J, 31 on chromosome U, 34 on chromosome E and 43 on chromosome O. Seven principal patterns of puffing activity were defined taking into account the different curves of the puffing histograms. Gene activities per chromosome as well as total were analysed. Three peaks of gene activity at the beginning, middle and ending of prepupation can …
Differences in gene activity in a Drosophila species cluster belonging to the Obscura group
1993
The polytene chromosome puffing pattern of Drosophila madeirensis was established and compared with those of the related species D. subobscura and D. guanche. A total of 145 loci, active in some of the 12 developmental stages analysed, were described, 38 of which were found to form the puffing pattern characteristic to this species. Taking into account the number of puffs as well as the mean puff expression, D. madeirensis shows a similar activity level to D. guanche, both species being less active than D. subobscura. The low gene activity of D. madeirensis and D. guanche was explained as a consequence of their ecological characteristics.
Karyotype analysis, nucleolar organizer regions(NORs), and C-banding pattern of Dicentrarchus iabrax(L.) and Dicentrarchus punctatus(Block, 1792)(Pis…
1990
Chromosomes of Dicentrarchus labrax and Dicentrarchus punctatus collected from the Gulf of Palermo are examined from kidney cells. The diploid chromosome number in both species is 2n=48. Ag-NOR and C-banding analyses revealed the presence of structural chromosomal polymorphism involving pair 1.A comparative analysis among the Giemsa, NOR- and C-banded karyotypes suggests that a close phylogenetic relationship between D. labrax and D. punctatus occurs. There are evidences for a conservative evolutionary trend in this genus.
Spermatocyte chromosome banding studies inBuccinulum corneum (Prosobranchia: Neogastropoda): Variation in silver-NOR banding pattern
1990
Diploid number (2n=72), and haploid number (n=36) forBuccinulum corneum (L. 1758) collected from the Gulf of Palermo in December 1987 were determined. A simple method to obtain nucleolar organizer regions (NOR), and constitutive heterochromatin regions (C-bands) of chromosomes ofB. corneum is described. Analyses of silver-stained chromosome preparations ofB. corneum suggest that a within-individual variability in NOR-banding pattern is present in each of the five specimens analysed.
Genomic structure and paralogous regions of the inversion breakpoint occurring between human chromosome 3p12.3 and orangutan chromosome 2.
2003
Intrachromosomal duplications play a significant role in human genome pathology and evolution. To better understand the molecular basis of evolutionary chromosome rearrangements, we performed molecular cytogenetic and sequence analyses of the breakpoint region that distinguishes human chromosome 3p12.3 and orangutan chromosome 2. FISH with region-specific BAC clones demonstrated that the breakpoint-flanking sequences are duplicated intrachromosomally on orangutan 2 and human 3q21 as well as at many pericentromeric and subtelomeric sites throughout the genomes. Breakage and rearrangement of the human 3p12.3-homologous region in the orangutan lineage were associated with a partial loss of dup…
Genetic aspects in hominid evolution
2000
Genomic comparison between apes and humans have made important contributions to our understanding of human evolution. The modern period of karyological comparisons between humans and other primates began about forty years ago and has been marked by a series of technical revolutions. In the 1960s pioneering genetic and chromosomal comparisons of human and great apes suggested, as had Darwin a century before, that our closest relative were the African apes. Early immunological analyses placed human/apes divergence at about five million year ago. Acceptance of man’s late divergence from the African apes was delayed by the scarcity of paleontological evidence coupled with a fallacious Asiatic o…
Human cytochrome P450 reductase can act as a source of endogenous oxidative DNA damage and genetic instability.
2005
Studies with repair-deficient mice and other experiments suggest that oxidative DNA modifications are generated in all types of cells even under physiological conditions and that this type of endogenous DNA damage contributes to spontaneous cancer incidence. However, the cellular sources of reactive oxygen species that are relevant for nuclear oxidative DNA damage are largely unknown. Here, we report that expression of human NADPH-cytochrome P450 reductase (hOR) in cultured V79 Chinese hamster cells gives rise to elevated basal levels of oxidative purine modifications after depletion of glutathione. Also, the basal levels of micronuclei are increased in the hOR-expressing cells, and again t…
Simultaneous Aurora-A/STK15 overexpression and centrosome amplification induce chromosomal instability in tumour cells with a MIN phenotype
2007
Abstract Background Genetic instability is a hallmark of tumours and preneoplastic lesions. The predominant form of genome instability in human cancer is chromosome instability (CIN). CIN is characterized by chromosomal aberrations, gains or losses of whole chromosomes (aneuploidy), and it is often associated with centrosome amplification. Centrosomes control cell division by forming a bipolar mitotic spindle and play an essential role in the maintenance of chromosomal stability. However, whether centrosome amplification could directly cause aneuploidy is not fully established. Also, alterations in genes required for mitotic progression could be involved in CIN. A major candidate is represe…
CENPA overexpression promotes genome instability in pRb-depleted human cells
2009
Abstract Background Aneuploidy is a hallmark of most human cancers that arises as a consequence of chromosomal instability and it is frequently associated with centrosome amplification. Functional inactivation of the Retinoblastoma protein (pRb) has been indicated as a cause promoting chromosomal instability as well centrosome amplification. However, the underlying molecular mechanism still remains to be clarified. Results Here we show that pRb depletion both in wild type and p53 knockout HCT116 cells was associated with the presence of multipolar spindles, anaphase bridges, lagging chromosomes and micronuclei harbouring whole chromosomes. In addition aneuploidy caused by pRb acute loss was…
Abnormal mitotic spindle assembly and cytokinesis induced by D-Limonene in cultured mammalian cells
2013
D-Limonene is found widely in citrus and many other plant species; it is a major constituent of many essential oils and is used as a solvent for commercial purposes. With the discovery of its chemotherapeutic properties against cancer, it is important to investigate the biological effects of the exposure to D-Limonene and elucidate its, as yet unknown, mechanism of action. We reported here that D-Limonene is toxic in V79 Chinese hamster cells in a dose-dependent manner. Moreover, to determine the cellular target of D-Limonene, we performed morphological observations and immunocytochemical analysis and we showed that this drug has a direct effect on dividing cells preventing assembly of mito…