A diagram of the process of cell division by mitosis.
Click on image for full size
Courtesy of National Center for Biotechnology Information, NIH

How New Cells Are Made

Some organisms, like animals and plants need to make more cells to grow larger. To grow, one cell divides into two identical cells. Other organisms, like protists, have only one cell. They can reproduce by splitting their one cell into two or more.

Before dividing, the cellís genetic material, called chromosomes, needs to duplicate forming two identical sets. The two sets of chromosomes are divided during a process called mitosis, which is a four-step process.

Step 1:
During this step the cell gets ready. Duplicated chromosomes are held together and change from thin threads into thick rods. Fibers form to help pull the pairs of chromosomes apart.

Step 2:
The thin wall called a membrane that surrounds the nucleus brakes apart. The chromosomes are no longer trapped within it. Instead, they line up at the middle of the cell. The fibers become stronger and attach at both ends of the cell as well as to each chromosome.

Step 3:
During this step, the action really happens! Those thick fibers attached to two ends of the cell pull the chromosomes into two groups.

Step 4:
A membrane forms around both groups of chromosomes and the rest of the cell begins to divide. With the same genetic material, these two cells are just like the one they were made from!

Last modified April 13, 2004 by Lisa Gardiner.

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