cell cycle


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Related to cell cycle: cell division, mitosis, meiosis

Cell cycle

The succession of events that culminates in the asexual reproduction of a cell; also known as cell division cycle. In a typical cell cycle, the parent cell doubles its volume, mass, and complement of chromosomes, then sorts its doubled contents to opposite sides of the cell, and finally divides in half to yield two genetically identical offspring. Implicit in the term “cycle” is the idea that division brings the double-sized parent cell back to its original size and chromosome number, and ready to begin another cell cycle. This idea fits well with the behavior of many unicellular organisms, but for multicellular organisms the daughter cells may differ from their parent cell and from each other in terms of size, shape, and differentiation state.

The time required for completion of a eukaryotic cell cycle varies enormously from cell to cell. Embryonic cells that do not need to grow between divisions can complete a cell cycle in as little as 8 min, whereas cycling times of 10–24 h are typical of the most rapidly dividing somatic cells. Many somatic cells divide much less frequently; liver cells divide about once a year, and mature neurons never divide. Such cells may be thought of as temporarily or permanently withdrawing from the cell cycle.

Eukaryotic phases

The cell cycle is divided into two main parts: interphase and mitosis (see illustration). During interphase, the cell grows and replicates its chromosomes. Interphase accounts for all but an hour or two of a 24-h cell cycle, and is subdivided into three phases: gap phase 1 (G1), synthesis (S), and gap phase 2 (G2). Interphase is followed by mitosis (nuclear division) and cytokinesis (cell division). This relatively brief part of the cell cycle includes some of the most dramatic events in cell biology.

Phases of the eukaryotic cell cycleenlarge picture
Phases of the eukaryotic cell cycle

G1 phase

Gap phase 1 begins at the completion of mitosis and cytokinesis and lasts until the beginning of S phase. This phase is generally the longest of the four cell cycle phases and is quite variable in length. During this phase, the cell chooses either to replicate its deoxyribonucleic acid (DNA) or to exit the cell cycle and enter a quiescent state (the G0 phase).

S phase

Replication of the chromosomes is restricted to one specific portion of interphase, called S phase (DNA synthesis phase), which typically lasts about 6 h. In mammalian cells, the start of S phase—the actual initiation of DNA synthesis—takes place several hours after the cell has committed to carrying out DNA synthesis. During S phase, each chromosome replicates exactly once to form a pair of physically linked sister chromatids. In animal cells, a pair of centrioles is also duplicated during S phase. See Chromosome, Genetics

G2 phase

The portion of interphase that follows S phase is called gap phase 2. Some cells can exit the cell cycle from G2 phase, just as they can from G1 phase.

M phase

M phase includes the overlapping processes of mitosis and cytokinesis. Mitosis is divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Cytokinesis usually begins during anaphase and ends at a point after the completion of mitosis. At the end of cytokinesis, the parent cell has formed its two G1 phase progeny and the cell is ready to repeat the cycle. See Cytokinesis, Mitosis

Control of cell cycle

The network of proteins that regulate DNA synthesis (G1/S), mitotic entry (G1/M), and mitotic exit (the transition from mitotic metaphase to anaphase and then out of mitosis) appears to be well conserved throughout eukaryotic evolution. At the heart of these cell cycle transtions is the periodic activation and inactivation of cyclin-dependent protein kinases. In addition, in multicellular eukaryotes, pathways regulating entry into and exit from the cell cycle entrain these central cyclin-dependent kinases to extrinsic signals.

cell cycle

[′sel ‚sī·kəl]
(cell and molecular biology)
In eukaryotic cells, the cycle of events consisting of cell division, including mitosis and cytokinesis, and interphase.
References in periodicals archive ?
Table S3: correlations between the PLK1 expression levels and the cell cycle activity in 33 TCGA cancer types.
However, raising the calcium concentration to 1.0mM resulted in stratification as well as differentiation and stratification is generally held to involve the reduction in the affinity of the extracellular matrix receptors, the integrin for their ligands, which include FN.10 in the present study it was first investigated whether the cells exited the cell cycle in these different calcium concentrations by staining the cultures with Ki67, an antibody specific for cells in cycle.
Overall, this suggests that DAC induces cell cycle arrest in SKM-1 cells and that the observed upregulation of CDKN1A and CDKN1B is dependent on FOXO3A, but that DAC-induced MYC downregulation is not dependent on active FOXO3A.
The sevoflurane neurotoxicity may be due to the decrease in cell cycle exit and increase in the S-phase duration of neural progenitors, which consequently lead to proliferation inhibition and differentiation abnormality in the fetal PFC.
The regulation of cell cycle arrest on TNA surface was further investigated involving multiple genes, namely, CHEK1, CHEK2, TP53, MYC, GADD45G, and GADD45A, at mRNA expressions level (Figure 4(a)).
Uncontrolled cell proliferation, apoptosis, cell cycle, and enhanced cell migration are the key features of tumor cells and also the important therapeutic targets.
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Cyclin-dependent kinases (CDKs) contains kinase domain with little kinase activity but on binding with Cyclin, the Cyclin/CDK become an active complex and cause the hyperphosphorylation of pRB that ultimately involve in regulation of transcription and mRNA processing while Cyclin/CDK complex is itself regulated by cell cycle inhibitors of the INK4 (inhibitors of CDK4) and CIP/KIP (CDK interacting protein/kinase inhibitory protein) families, especially p16Ink4a and p21Cip1 (Dyer and Bremner, 2005; Sage, 2012).
Conclusions: Honokiol can repress human glioma growth by inducing apoptosis and cell cycle arrest in tumor cells though activating a p53/cyclin D1/CDK6/CDK4/E2F1-dependent pathway.
Cells were treated with either the LBE or with a corresponding vehicle control in experiments assessing proliferation rate of cancer cells, cell cycle analysis, measurement of extracellular reactive oxygen species (ROS), measurement of intracellular ROS, fluorescence microscopy and immunoblotting.
Following the rollout of the new biology lab equipment, students took turns peering into the eyepieces of the new microscopes after obtaining slides from Eddie Dry, assistant professor of biology, and being directed to locate and identify the various phases of the cell cycle. Dry moved throughout the lab working one-on-one with the 23 students to ensure all were able to successfully locate cell cycle phases.

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