Question

Processes taking part in cell cycle regulation(please give also examples)

Answer 1

The regulation of the cell cycle occurs through checkpoints and cyclins.

Checkpoints are basically control points where the cycle can be regulated. Checkpoints, as the name implies, allow the cell to verify if everything is okay or not before continuing along the path to cell division. There are three main checkpoints.

The first is the G1, or restriction point. This occurs during the G1 phase. Environmental cues and extracellular signals either tell the cell to divide, or if conditions are not favorable, to remian in the G0 phase. The second is the G2 checkpoint. This checkpoint ensures that the cell is ready for mitosis. At this stage, the cell asks: Has DNA replication occurred successfully? Are environmental conditions still favorable for division? If yes - mitosis begins! A final checkpoint, the M point, occurs before anaphase, during metaphase. The question here is simply: are all of the chromosomes lined up and attached to fibers?

Cyclins and cyclin-dependent kinases are simply the main messengers carrying out the "go" signal of the checkpoints. For example, if the cell receives a "go" signal at the G2 checkpoint, the cyclin and its associated kinase form a complex called the MPF which activates various pathways leading into mitosis.

Answer 2

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