More About Mitosis and Cytokinesis

 

 

2 terms you should be familiar with:

chromatin-long, thin, readable strands of DNA, usually found in the cell during interphase

chromosomes-thickened, coiled strands of DNA, found in cells during cell division.  Chromosomes are easily distinguishable with a light microscope.  DNA is very organized when found in chromosomes so each new cell will end up with the exact same DNA. (see drawing below)

 

Mitosis can be divided into 4 phases:

1) prophase

2) metaphase

3) anaphase

4) telophase

 

Prophase-Nuclear membrane disappears.  Chromosomes become visible.  Spindle fibers begin to form.

 

 

 

 

 

 

 

 

 

 

 

 

 

Metaphase-Chromosomes line up along the equator, or center of the cell.  Spindle fibers attach to the centromere of each chromosome.

Anaphase-Spindle fibers begin to pull chromatids apart.

Telophase-Chromatids are pulled to opposite poles of the cell.  Spindle fibers disappear.  Cytokinesis begins.  DNA stretches out to form chromatin.  Nuclear membrane reforms.

 

 

 

During cytokinesis in plant cell, a cell plate forms (like in the diagrams above).  In an animal cell, a cleavage furrow forms during cytokinesis to split the cell.

 

 

After the cell has divided, the two new identical cells begin interphase!

                                    new cell 1                                 new cell 2

                    

 

Why do cells divide?

1) organism is growing or developing

2) to heal injury or repair worn out cells

3) surface area to volume ratio gets too small (look at lab activity)