Lesson 3: Eukaryotic cell cycle and Mitosis
Instructions:
1. Read through the fact file and summarise into one page, you only need to include the things you
don't already know – you should be familiar with some of this topic from GCSE.
2. Complete questions on fact file sheet, self-assess in green. Please don't just tick random things,
tick/underline the exact thing you got right. Highlight what you got wrong.
3. Answer exam questions and again self-assess.
4. Attach a copy of your work.
Fact file
The eukaryotic cell cycle
This is illustrated by Fig 1.
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.
The total time of the cell cycle varies from around 30 minutes in growing yeast cells, 18 to 24 hours in animal sperm-
producing cells, 10 to 30 hours in plant meristematic cells to several weeks in slowly regenerating tissues.
For example in a cell with a 24 hour cycle the times of the phases would be around G1 10 hours, S 9 hours, G2 4
hours and mitosis with cytokinesis 1 hour.
Fully differentiated cells generally remain arrested in the G1 stage and will not normally divide again. Some cells
remain arrested in the G2 stage, for example, human cardiac muscle cells. The synthesis of DNA occurs in the S
phase when the quantity of DNA in the cell is doubled. This is shown in Fig 2.
