The Cell Cycle and
Mitosis
SNC2P
The Cell Cycle

Every hour,
approximately 1 billion
of your cells die – but
approximately 1 billion
cells are created in a
process of cell division
called mitosis.
Interphase

The cell prepares for cell
division by growing and
by making copies of its
organelles and DNA.
Interphase
The cell prepares for cell
division by growing and
by making copies of its
organelles and DNA.
 This stage of the cell
cycle is called
interphase.

Prophase

During the first phase of mitosis, prophase,
the DNA condenses into chromosomes and
the nucleus disintegrates. A framework
called the mitotic spindle forms.
Metaphase

Then the chromosomes line up in the
middle of the cell. This is metaphase.
Anaphase

During anaphase, the chromosomes
separate and are pulled to opposite
ends of the cell.
Telophase and Cytokinesis

In the last stage of mitosis, telophase, the cell
divides the cytoplasm into two portions.
Telophase and Cytokinesis
In the last stage of mitosis, telophase, the cell
divides the cytoplasm into two portions.
 The final separation of the cytoplasm into two
distinct cells is called cytokinesis.

Rate of Mitosis
Different parts of an organism experience
different rates of mitosis (e.g. an onion root
tip is where growth occurs and therefore the
cells divide frequently, every 12 – 36 hours).
Rate of Mitosis
In humans, skin cells (that brush off) or
intestinal cells (that are broken down by the
digestive process) have high rates of mitosis,
but red blood cells may last for months.
human skin cells
Apoptosis
The controlled death of a cell that is no longer
useful (e.g. white blood cells post-infection)
or is damaged is called apoptosis.
Your Task

Your task will be to identify the structures that
will allow you to identify each phase and then
to observe mitosis in a prepared slide of an
onion root tip.