Identifying Phases of Mitosis
- Cells undergoing different stages of the cell cycle can be identified using photomicrographs taken from microscope slides
- Cells undergoing certain stages of the cell cycle have distinctive appearances
Interphase
- As cells spend the majority of the cell cycle in this stage then most cells will be in this stage
- The chromatin is visible (however chromosomes are not) so the nuclei have a dark appearance
Prophase
- Chromosomes are visible
- The nuclear envelope is breaking down
Metaphase
- Chromosomes are lined up along the middle of the cell
Anaphase
- Chromosomes are moving away from the middle of the cell, towards opposite poles
- As they are pulled from the centromere through the cytoplasm, the chromosomes tend to have a characteristic 'V' shape
Telophase
- Chromosomes have arrived at opposite poles of the cell
- Chromosomes begin to uncoil (are no longer condensed)
- The nuclear envelope is reforming
Cytokinesis
- Animal cells: a cleavage furrow forms and separates the daughter cells
- Plant cells: a cell plate forms at the site of the metaphase plate and expands towards the cell wall of the parent cell, separating the daughter cells
Identification of phases
Micrograph showing a cell undergoing prophase (P)
Micrograph showing cells undergoing metaphase (M) and anaphase (A)
Micrograph showing cells undergoing metaphase (M) and anaphase (A)
Micrograph showing a cell undergoing anaphase (A)
Examiner Tip
It is important to be able to recognise each mitotic stage from electron micrographs and to be able to explain why that cell is in the stage you have selected. It can be difficult to tell prophase and telophase apart in some photomicrographs. In prophase, there is only one group of chromosomes in the cell while in telophase there are two groups, one at each pole.
