Modelling Mitosis

 

Early Interphase

 

Interphase is the longest stage in the cell cycle. This is a time when a cell carries out its various functions within the organism.

Growth and preparation

• During the first phase of interphase, a cell expands in size and makes the proteins and molecules necessary for the cell to function. Some organelles begin to duplicate.

 

 

 

 

Late interphase (replication)

 

At this stage, the DNA copies or makes a “replica” of itself in a process called Replication. The DNA is being replicated by the enzyme that splits the DNA sides, then the new bases are paired with the bases on the original DNA. There is now 2 identical DNA molecule produced.

 

 

 

 

 

 

Prophase

 

The replicated chromosomes coil up into x-shaped chromosomes. The nucleolus will disappear and spindle fibers form, and then the spindle fibers attach to the centromeres of the chromosomes. During the late prophase stage, the spindle fiber is completely formed and the chromosomes’ centromeres attach to the spindle fibers.

 

 

 

Metaphase

 

The tugging action of the spindle fibers pulls the x-shaped chromosomes into a single line across the middle (or equator) of the cell.

 

 

 

 

Anaphase

 

The spindle fibers begin to contract and shorten. This action pulls the centromere apart, allowing the sister chromatids to move to opposite poles of the cell. Once the separate, each sister chromatid is considered to be a chromosome.

 

 

 

 

Telophase

 

In the final stage of mitosis, one complete set of chromosomes is now at each pole of the cell. The spindle fibers begin to disappear, and a nuclear membrane forms around each set of chromosomes. A nucleolus appears within each nucleus. Now there are two nuclei in one cell, and the cell is ready to divide.

 

 

 

 

 

 

Cytokinesis

 

The final stage of the cell cycle is called cytokinesis. Cytokinesis separates the two nuclei into two daughter cells. These newly formed cells are identical original parent cell.