What is Mitosis?


There are various structures within the cell, but many are too difficult to see. For example, within the nucleus lie the chromosomes. These are important for heredity and reproduction. When a cell splits and becomes two, certain processes occur within the nucleus first.  One of these processes involves the splitting of the chromosomes.  


In the drawings below, you can see the chromosomes in the nucleus going through the process called mitosis, or division.  If you have a microscope (400x) and a properly stained slide of the Onion root tip (or Allium root tip), you can see the phases in different cells, frozen in time.  You will be looking at strands of DNA inside the cell!  Note: The onion root tip slide is included free in your slide kit when you purchase a microscope from Microscope World.


The Phases of Mitosis

Prophase mitosis

Metaphase mitosis

First Phase:
Called Prophase, the DNA molecules of the
chromosomes condense.
Second Phase:
Called Metaphase, the chromosomes line up in the center of the cell, separate and become a pair of identical chromosomes.

Anaphase mitosis

Third Phase:
Called Anaphase, each set of chromosomes moves
toward the opposite end of the cell.
Fourth Phase:
Called Telophase, the spindle fibers disappear, the nuclear membrane appears and the cell divides into two daughter cells.
When a cell divides, first the chromosomes split and become two. Each new one looks exactly like the original old one. Then the chromosomes move away from each other and become two similar nuclei. Finally, the cell splits in two, making two new identical cells, each with an identical nucleus.
microscope specimen
At left is an actual picture of an onion root tip specimen. Can you identify the phase of the chromosomes in the center that look like a spider? (Answer below)

To remember the names of the phases in order, visualize a floor mat with a big letter "P" inscribed on it. When you see this image, think of the word "PMAT"

You will be likely tested on this in a high school biology class!

More interesting information:   Many cells of the same kind are called tissue. Blood is a tissue. When many different kinds of cells work together, we get an organ, like a heart. Finally, when many organs work together, they form a complex living thing, like a flower, a flea, or a human. Think of all the different types of cells and organs working together to keep you alive!

Answer to question above:  metaphase

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