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Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism , gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis.
The G 1 phase, gap 1 phase, or growth 1 phase, is the first of four phases of the cell cycle that takes place in eukaryotic cell division. In this part of interphase, the cell synthesizes mRNA and proteins in preparation for subsequent steps leading to mitosis. G 1 phase ends when the cell moves into the S phase of interphase.
Fig. 2 Irreversible and bistable switch in mitotic exit with control parameter being Sic1 level and order parameter being cell cycle phases. Because eukaryotic cell cycle involves a variety of proteins and regulatory interactions, dynamical systems approach can be taken to simplify a complex biological circuit into a general framework for ...
Rb without a phosphate, or unphosphorylated Rb, regulates G0 cell cycle exit and differentiation. During the beginning of the G1 phase, growth factors and DNA damage signal for the rise of cyclin D levels, which then binds to Cdk4 and Cdk6 to form the CyclinD:Cdk4/6 complex. [11] This complex is known to inactivate Rb by phosphorylation.
Initiation of the centrosome cycle occurs early in the cell cycle in order to have two centrosomes by the time mitosis occurs. Since the centrosome organizes the microtubules of a cell, it has to do with the formation of the mitotic spindle, polarity and, therefore, cell shape, as well as all other processes having to do with the mitotic ...
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. Endoreduplication 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 ...
During each cell cycle, it is important that the genome be completely replicated once and only once. Formation of the pre-replication complex during late M and early G1 phase is required for genome replication, but after the genome has been replicated the pre-RC must not form again until the next cell cycle.
The cell division cycle protein 20 homolog is an essential regulator of cell division that is encoded by the CDC20 gene [5] [6] in humans. To the best of current knowledge its most important function is to activate the anaphase promoting complex (APC/C), a large 11-13 subunit complex that initiates chromatid separation and entrance into anaphase .