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The Cell Cycle

Biology (Year 12) - Continuity of Life: Processes

Ben Whitten

What is the cell cycle?

"MITOSIS, CYTOKINESIS, AND THE CELL CYCLE by Neural Academy (Aug, 2019)"

Image: Simple cell cycle image, Image by Simon Caulton, Sourced Under a Creative Commons 4.0 License from Wiki Commons The cell cycle can be described as the ordered sequence of events in the life of a cell, beginning from when the cell is formed from its parent cell and is then completed with its own division. The cell cycle takes place between cell divisions, and the whole process collectively comes under interphase.

What are the phases of the cell cycle?

1. G1 phase: This first growth phase is a period of metabolic activity and growth, in which new proteins are made. This phase ends when DNA begins to replicate. 2. S phase: This phase, otherwise known as the 'synthesis' phase, is when DNA replication takes place. The cell synthesises a complete copy of DNA in the nucleus, and centrosomes are duplicated. 3. G2 phase: In this second growth phase, the cell grows larger, creating more proteins and organelles. The cell reorganises its contents in preparation for mitosis, the 'M' phase to occur. 4. M phase: This phase is only a small part of the whole cell cycle, and is where cell division actually occurs, which forms new daughter cells. This phase also contains the process of cytokinesis. Extra: G0 phase: This phase includes cells which are in a non-proliferating state. The cell is undergoing an extended G1 phase, but is not preparing to replicate its DNA for cell division to occur. There are some important things to note regarding the cell cycle. In reality, the cell cycle is a continuous process which is divided into phases for simplicity. The length of the cell cycle is also varied depending on the cell type. During development and in area of high wear-and-tear, such as the skin, cells divide at a faster rate. It's also important to note that some cells do not divide at all, therefore not undergoing the cell cycle, for example nerve and retinal cells.

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