The Cell Cycle
Biology: IB Diploma Higher Level, topic 2.4.1
The Cell Cycle
We have already seen that not all cells can divide (e.g. viruses need a host cell to divide). Eukaryotic cells that have the ability to divide have a cell cycle.
The cell cycle
- Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages of growth, DNA replication, and division.
- This is called the cell cycle.
Phases of the cell cycle
- The cell cycle has two major phases: interphase and the mitotic phase.
- During interphase, the cell grows and DNA is replicated.
- During the mitotic phase, the replicated DNA and cytoplasmic contents are separated, and the cell divides.
- There are two types of cell division in eukaryotes: mitosis and meiosis.
Interphase
- Interphase is subdivided into three growth stages called G1, S and G2 stage.
- In G1, the cell is accumulating the building blocks of chromosomal DNA and the associated proteins. The cell is also accumulating sufficient energy reserves to complete the task of replicating each chromosome in the nucleus.
- In S, DNA synthesis happens.
- In G2, the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation.
The mitotic phase
- Mitosis is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication.
- Multicellular organisms go through mitosis to grow and repair damaged tissues.
G0
- Sometimes cells enter a Gap zero (G0) phase, during which they do not actively prepare to divide.
- The G0 phase can be temporary until triggered by an external signal to enter G1, or permanent, such as mature cardiac muscle cells and nerve cells.
Test yourself on The Cell Cycle
Which of the following statements regarding the cell cycle are true?