4.1: The Cell Cycle
The cell cycle is made up of three main stages; interphase, mitosis, and cytokinesis.
These stages can be organized into five general phases or processes.
Mitosis is the division of the genetic material into two complete and separate sets.
Cytokinesis is the division of the cytoplasm and the organelles into two separate cells.
Two new daughter cells with the same genetic information as the parent cell are formed.
1. Refer to the diagram above. Summarize the events occurring at each stage in the
cell cycle.
a) Interphase
b) G1 phase
c) S phase
d) G2 phase
e) Mitosis
f) Cytokinesis
2. What is the main purpose of the cell cycle in human skin cells?
3. How would the cell cycle in actively dividing cells differ from the cell cycle in
cells that no longer divide?
4.1: Mitosis and Cytokinesis
Mitosis – is the process of nuclear division. The linked processes of mitosis and
cytokinesis have three important functions:
a) growth of multicellular organisms
b) replacing worn out or dead cells
c) regenerating damaged tissues
To accomplish these tasks, each new daughter cell must have the correct genetic
information. This means that:
1. The genetic material of the parent cell must be replicated. This process takes
place during the S phase of the cell cycle (Interphase)
2. The replicated chromatin must be condensed and organized as chromosomes
in the nucleus. The resulting genetically identical sister chromatids are held
together at the centromere.
3. The sister chromatids separate during mitosis.
There are two major differences between mitosis of animal cells and mitosis of plant cells.
1. In animal cells, spindle apparatus forms from the centrioles. Plant cells do
not have centrioles. They do, however, form a spindle apparatus.
2. During cytokinesis in animal cells, the cell membrane indents to form two
daughter cells (cleaving). In plant cells, a cell plate develops to form two
daughter cells.