Synthesis (cell Cycle)
S phase (Synthesis Phase) is the phase of the cell cycle in which DNA is DNA replication, replicated, occurring between G1 phase, G1 phase and G2 phase, G2 phase. Since accurate duplication of the genome is critical to successful cell division, the processes that occur during S-phase are tightly regulated and widely conserved. Regulation Entry into S-phase is controlled by the G1 restriction point (R), which commits cells to the remainder of the cell-cycle if there is adequate nutrients and growth signaling. This transition is essentially irreversible; after passing the restriction point, the cell will progress through S-phase even if environmental conditions become unfavorable. Accordingly, entry into S-phase is controlled by molecular pathways that facilitate a rapid, unidirectional shift in cell state. In yeast, for instance, cell growth induces accumulation of Cln3 cyclin, which complexes with the Cyclin-dependent kinase, cyclin dependent kinase CDK2. The Cln3-CDK2 complex ...
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Asymmetry In The Synthesis Of Leading And Lagging Strands
Asymmetry is the absence of, or a violation of, symmetry (the property of an object being invariant to a transformation, such as reflection). Symmetry is an important property of both physical and abstract systems and it may be displayed in precise terms or in more aesthetic terms. The absence of or violation of symmetry that are either expected or desired can have important consequences for a system. In organisms Due to how cell (biology), cells divide in organisms, asymmetry in organisms is fairly usual in at least one dimension, with symmetry (biology), biological symmetry also being common in at least one dimension. Louis Pasteur proposed that biological molecules are asymmetric because the cosmic [i.e. physical] forces that preside over their formation are themselves asymmetric. While at his time, and even now, the symmetry of physical processes are highlighted, it is known that there are fundamental physical asymmetries, starting with time. Asymmetry in biology Asym ...
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