Cell Division and Mitosis Biology Diagrams The length of the cell cycle is highly variable, even within the cells of a single organism. In humans, the frequency of cell turnover ranges from a few hours in early embryonic development, to an average of two to five days for epithelial cells, and to an entire human lifetime spent in G 0 by specialized cells, such as cortical neurons or cardiac muscle cells.
Cell cycle control is focused mainly on two events, the replication of genomic DNA and its subsequent segregation between daughter cells, which in eukaryotic cells occur during distinct cell cycle
Core control principles of the eukaryotic cell cycle Biology Diagrams
To prevent a compromised cell from continuing to divide, there are internal control mechanisms that operate at three main cell cycle checkpoints at which the cell cycle can be stopped until conditions are favorable. Figure 1 The cell cycle is controlled at three checkpoints. Integrity of the DNA is assessed at the G1 checkpoint.
The cell-cycle control system was simply a black box inside the cell. It was not even clear whether there was a separate control system, or whether the processes of DNA synthesis, mitosis, and cytokinesis somehow controlled themselves. A major breakthrough came in the late 1980s with the identification of the key proteins of the control system
Regulation of Cell Cycle Entry and Exit: A Single Cell Perspective Biology Diagrams
Cyclin-dependent kinases (CDKs) lie at the heart of eukaryotic cell cycle control, with different cyclin-CDK complexes initiating DNA replication (S-CDKs) and mitosis (M-CDKs)1,2. However, the Cell cycle checkpoints secure ordered progression from one cell cycle phase to the next. They are important to signal cell stress and DNA lesions and to stop cell cycle progression when severe problems occur. Recent work suggests, however, that the cell cycle control machinery responds in more subtle and sophisticated ways when cells are faced with naturally occurring challenges, such as CONTROL OF THE CELL CYCLE Cyclin‐dependent kinase (CDK) regulation. The transition from one cell cycle phase to another occurs in an orderly fashion and is regulated by different cellular proteins. Key regulatory proteins are the cyclin‐dependent kinases (CDK), a family of serine/threonine protein kinases that are activated at specific
