La divisió cel·lular i la construcció de les idees

La divisió cel·lular és un procés fonamental per a la vida, l’estudi del qual ha captat l’atenció dels biòlegs cel·lulars des del final del segle xix. Al llarg de molts anys de recerca, hem aconseguit tenir un dibuix de la divisió cel·lular més ampli, tot i que no complet, que el que van esbossar els primers observadors

Особливості каріології представників родини Bithyniidae (Mollusca: Gastropoda: Pectinibranchia) фауни України

Досліджено каріотипи п’ять видів родини Bithyniidae фауни України: B. (Bithynia) curta; B. (Milletelona) decipiens; B. (Bithynia) produсta; B. (Bithynia) tentaсulata; Digyrcidum bourguignati. Кількість хромосом у всіх видів становить 17 пар, хромосомна формула представлена метацентричними, субметацентричними та субтелоцентричними морфологічними типами хромосом. Основне число NF=68. Проаналізовано можливість використання морфологічних типів хромосом, середніх значень центромерного індексу та абсолютної довжини хромосом як інтегруючих та диференціюючих факторів в межах родини Bithyniidae. Виявлено по одній маркерній хромосомі для кожного досліджуваного виду. Решта хромосомних пар за своєю морфологічною структурою виявилися подібними для видів родини Bithyniidae

Ueber Karyokinese

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The architecture of chicken chromosome territories changes during differentiation

BACKGROUND: Between cell divisions the chromatin fiber of each chromosome is restricted to a subvolume of the interphase cell nucleus called chromosome territory. The internal organization of these chromosome territories is still largely unknown. RESULTS: We compared the large-scale chromatin structure of chromosome territories between several hematopoietic chicken cell types at various differentiation stages. Chromosome territories were labeled by fluorescence in situ hybridization in structurally preserved nuclei, recorded by confocal microscopy and evaluated visually and by quantitative image analysis. Chromosome territories in multipotent myeloid precursor cells appeared homogeneously stained and compact. The inactive lysozyme gene as well as the centromere of the lysozyme gene harboring chromosome located to the interior of the chromosome territory. In further differentiated cell types such as myeloblasts, macrophages and erythroblasts chromosome territories appeared increasingly diffuse, disaggregating to separable substructures. The lysozyme gene, which is gradually activated during the differentiation to activated macrophages, as well as the centromere were relocated increasingly to more external positions. CONCLUSIONS: Our results reveal a cell type specific constitution of chromosome territories. The data suggest that a repositioning of chromosomal loci during differentiation may be a consequence of general changes in chromosome territory morphology, not necessarily related to transcriptional changes

The History of Cytological Studies by Aceto-carmine method

departmental bulletin pape

Cell Division: Single-Cell Physiology Reveals Secrets of Chromosome Condensation

Our understanding of higher order chromosome structure has been transformed through statistical mechanics-based computer simulations of polymer chains. A new study exploring basic electrostatic interactions demystifies how chromosomes regulate their state of compaction over several orders of magnitude. Our understanding of higher order chromosome structure has been transformed through statistical mechanics-based computer simulations of polymer chains. A new study exploring basic electrostatic interactions demystifies how chromosomes regulate their state of compaction over several orders of magnitude

Birth Defects Res A Clin Mol Teratol

HWI4/Intramural CDC HHS/United States2015-07-29T00:00:00Z24265126PMC451903

The role of PRDM9 gene in the process of DNA recombination

Pojava rekombinacije između dvaju homolognih kromosoma u mejozi je, skupa sa mutacijama, signifikantan parametar varijabilnosti u prirodi te same selekcije (njene efektivnosti i uspjeha). Frekvencija rekombinacije utječe na mnoge različite parametre populacijske genetike, poput strukture inbreedinga te pojave linkage disequilibriuma (LD). PRDM9 protein je koji sadrži ‘zinc finger’ domenu kojom se veže na DNA na specifičnim lokacijama unutar genoma, determinirajući time rekombinacijske hotspotove tijekom mejoze u mnogih vrsta. Na istima vrši trimetilaciju H3K4 i H3K36, reorganizirajući time nukleosomsku strukturu i stvarajući mjesto za formaciju DNA DSBa, potrebnog za razmjenu genetske informacije između homologa. Unatoč tomu što ovaj mehanizam nije u potpunosti objašnjen, najnovije tehnologije pomogle su razotkriti neke njegove dijelove te samim time sugerirati da je navedeni proces mnogo kompleksniji nego što se smatralo. Mnoge stvari još su nerazjašnjene u procesu mejotske rekombinacije, no sa brzim razvojem tehnologije više će pitanja biti postavljeno i odgovoreno daljnjim istraživanjima. Nadalje, PRDM9 gen ima veliku ulogu u nasljeđivanju te frekvencijama rekombinacija. Za primjer, PRDM9 aleli mogu utjecati na kromosomski razmještaj u ljudi, uzrokujući neke nasljedne bolesti.The appearance of recombination between homologous chromosomes in meiosis is, along with mutations, a significant parameter of the variability in nature, and furthermore, selection itself (and its efficiency and success). The frequency of recombination affects many different population-wise genetic parameters like genome inbreeding structure and the appearance of LD (linkage disequilibrium). PRDM9 is a zinc finger protein that binds DNA at specific locations in the genome where it trimethylates H3K4 and H3K36 at surrounding nucleosomes. During meiosis in many species, these actions determine the location of recombination hotspots. It also reorganizes local nucleosomal structure, creating a nucleosome-free center where the DNA DSB required for DNA exchange between chromosomes is formed. Although this mechanism wasn't completely clarified, the newest technologies helped discover parts of it and therefore suggest that this process is more complex than what was previously thought. A lot of things yet remain unknown in the process of meiotic recombination, but with rapid development of technology more questions will be asked and hopefully answers unveiled with further research. Furthermore, PRDM9 gene has a big role in inheritance and recombination frequencies. As an example, PRDM9 alleles influence human chromosomal rearrangements, causing hereditary diseases