The Cell Cycle
Biology: Cambridge International A Level, topic 5.1.2
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 grows.
- In S, DNA synthesis happens.
- In G2, the cell grows some more before the mitotic phases begins.
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.
Regulation of the cell cycle
- Internal checkpoints are important in the regulation of the cell cycle.
- At the first checkpoint (G1), DNA is checked to make sure there is no damage and the cell is checked to see if it is the correct size and has enough energy reserves.
- At the second checkpoint (G2), chromosomes are checked to make sure that they have all been replicated and none of the duplicated DNA is faulty.
- At the third checkpoint (M), sister chromatids are checked to confirm that their attachments to the spindle are suitable.
Test yourself on The Cell Cycle
Which of the following statements regarding the cell cycle are true?
How many checkpoints are involved in the regulation of the cell cycle?