The Eukaryotic cell cycle and Mitosis
This Factsheet covers the relevant AS syllabus content of the major examining boards. By studying this factsheet the candidate will gain a knowledge and understanding of:
• the different phases of the eukaryotic cell cycle (a eukaryotic cell has membrane bound organelles)
• the importances of mitosis
• the process of mitosis
The eukaryotic cell cycle
Fig 2. Quantity of DNA in the cell during different phases
This is illustrated by Fig 1.
DNA quantity/arbitrary units
Fig 1. The eukaryotic cell cycle
cell division G1 time G1
The G1, S and G2 phases are termed interphase. Interphase is the stage of the cell cycle between cell divisions. It is not a resting stage, since in an actively dividing and growing cell new DNA and proteins are being synthesised and in a non-dividing mature cell, the G1 or G2 cell is performing all its metabolic cell functions and specific jobs.
The importances of mitosis
Cell division consists of two phases, mitosis and cytokinesis. Mitosis, is the division of the nucleus. Cytokinesis is the division of the cytoplasm which usually, but not always, occurs immediately after nuclear division.
Only a small time period of the cell cycle consists of the cell division stages. The other phases, known as G1, S and G2 take up the majority of the time.
Cell division by mitosis is important during growth of eukaryotic organisms and is the way in which eukaryotes increase their cell numbers, either in a population of a single celled organism, such as Amoeba or yeast, or within the body of a multicellular organism. Growth may be allometric meaning that different parts of the organism grow at different rates. This can be due to mitosis occuring at different rates in different organs. Mitosis is also important during repair of damaged tissue.