Cell Division and Mitosis


Two things are needed for cell division: duplication and cytokinesis.

    The very precise duplication of genetic material.
The more imprecise separation of the cytoplasm, known as cytokinesis.

 

The duplication of genetic material has three key components. 

Genetic material within the nucleus is replicated.
The genetic material is packaged and separated into two new nuclei.
Each daughter cell gains exactly one copy of the genetic material.

 

Mitosis is the process of distributing exact copies of genetic information. 
It has six sub phases:  interphase, prophase, prometaphase, metaphase, anaphase, and telophase.


Interphase
interphase.gif (2756 bytes)

In interphase the nucleus replicates its DNA and centrosomes.
(This phase is comparable to the S-phase in the cell cycle)

 


Prophase
prophase.gif (3460 bytes)
During prophase, chromatin coils and condenses into chromosomes.
The centrosomes begin to migrate to opposite poles in the cell.
The spindle is formed as well.

 


Prometaphase

Prometaphase.gif (3412 bytes)

In prometaphase, the nuclear envelope breaks down,
and the centrosomes are positioned at opposite poles of the cell.
Kinetochore microtubules run from centromere to centrosomes

 


Metaphase

metaphase.gif (3747 bytes)

During metaphase, chromosomes line up in a plane within the cell

 


Anaphase

Anaphase.gif (3702 bytes)

In anaphase, the daughter chromatids are separated.
Microtubules shorten as the daughter chromatids move toward centrosomes.
Molecular motors pull the chromatids apart.

 


Telophase

telophase.gif (4355 bytes)

In Telophase, the chromatids reach the poles and the spindle begins to break down.
The nuclear envelop then reforms.

 

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