Endoréplication

Endoreduplication (also referred to as endoreplication or endocycling) is replication of the nuclear genome in the absence of mitosis, which leads to elevated nuclear gene content and polyploidy. Endoreplication can be understood simply as a variant form of the mitotic cell cycle (G1-S-G2-M) in which mitosis is circumvented entirely, due to modulation of cyclin-dependent kinase (CDK) activity. Examples of endoreplication characterized in arthropod, mammalian, and plant species suggest that it is a universal developmental mechanism responsible for the differentiation and morphogenesis of cell types that fulfill an array of biological functions. While endoreplication is often limited to specific cell types in animals, it is considerably more widespread in plants, such that polyploidy can be detected in the majority of plant tissues. Endoreplicating cell types that have been studied extensively in model organisms Endoreplication, endomitosis and polytenization are three somewhat different processes resulting in polyploidization of a cell in a regulated manner. In endoreplication cells skip M phase completely, resulting in a mononucleated polyploid cell. Endomitosis is a type of cell cycle variation where mitosis is initiated, but some of the processes are not completed. Depending on how far the cell progresses through mitosis, this will give rise to a mononucleated or binucleated polyploid cell. Polytenization arises with under- or overamplification of some genomic regions, creating polytene chromosomes. Based on the wide array of cell types in which endoreplication occurs, a variety of hypotheses have been generated to explain the functional importance of this phenomenon. Unfortunately, experimental evidence to support these conclusions is somewhat limited: Cell ploidy often correlates with cell size, and in some instances, disruption of endoreplication results in diminished cell and tissue size suggesting that endoreplication may serve as a mechanism for tissue growth.

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Gène

Un gène, du grec ancien (« génération, naissance, origine »), est, en biologie, une séquence discrète et héritable de nucléotides dont l'expression affecte les caractères d'un organisme. L'ensemble des gènes et du matériel non codant d'un organisme constitue son génome. Un gène possède donc une position donnée dans le génome d'une espèce, on parle de locus génique. La séquence est généralement formée par des désoxyribonucléotides, et est donc une séquence d'ADN (par des ribonucléotides formant de l'ARN dans le cas de certains virus), au sein d'un chromosome.

Prolifération cellulaire

La prolifération cellulaire est le fait que les cellules se multiplient rapidement et en abondance. Les cellules se reproduisent par mitose c’est-à-dire par division d'elles-mêmes, donc une cellule saine continue une lignée de cellules saines. Par contre, des cellules malades peuvent produire par exemple un cancer par division cellulaire. À l'inverse, l'expression du gène « aile vestigiale » inhibe cette prolifération cellulaire lors de la formation de l'aile de la drosophile.

Cell growth

Cell growth refers to an increase in the total mass of a cell, including both cytoplasmic, nuclear and organelle volume. Cell growth occurs when the overall rate of cellular biosynthesis (production of biomolecules or anabolism) is greater than the overall rate of cellular degradation (the destruction of biomolecules via the proteasome, lysosome or autophagy, or catabolism). Cell growth is not to be confused with cell division or the cell cycle, which are distinct processes that can occur alongside cell growth during the process of cell proliferation, where a cell, known as the mother cell, grows and divides to produce two daughter cells.

Explore la régulation du cycle cellulaire des mammifères, en mettant l'accent sur les événements entourant la transition des points R et les interactions clés des protéines.

Discute de la sélection naturelle, de l'origine de l'espèce, de la compatibilité de la reproduction, des barrières à l'écoulement des gènes, de la classification des espèces, des modes de spéciation et de la polyploïdie.

Explore les variations du nombre et de la structure des chromosomes, y compris les délétions, les duplications, les inversions et les translocations.

Robust designation of meiotic crossover sites by CDK-2 through phosphorylation of the MutS gamma complex

Alexander Woglar

Crossover formation is essential for proper segregation of homologous chromosomes during meiosis. Here, we show that Caenorhabditis elegans cyclin-dependent kinase 2 (CDK-2) partners with cyclin-like protein COSA-1 to promote crossover formation by promoti ...

NATL ACAD SCIENCES2022

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Protein concentration gradients pattern developing organisms and single cells. In Schizosaccharomyces pombe rod-shaped cells, Pom1 kinase forms gradients with maxima at cell poles. Pom1 controls the timing of mitotic entry by inhibiting Cdr2, which forms s ...

ELIFE SCIENCES PUBLICATIONS LTD2019

Cdk2 strengthens the intra-S checkpoint and counteracts cell cycle exit induced by DNA damage

Gérald Joseph Paul Lossaint, Katarina Bacevic

Although cyclin-dependent kinase 2 (Cdk2) controls the G1/S transition and promotes DNA replication, it is dispensable for cell cycle progression due to redundancy with Cdk1. Yet Cdk2 also has non-redundant functions that can be revealed in certain genetic ...

Springer Nature2017