Mitosis in an Onion Root Tip

The process of mitosis is cell reproduction of "regular" body cells. (Note: This is not sex cell reproduction.) Mitosis in an onion root cell is a common type of cell to view under the microscope because it is large and often you can view many different stages of mitosis in a single section of onion root tip. It is also common to stain the cells slightly to make the chromosomes more visible. The student will be looking for cells undergoing Interphase, prophase, metaphase, anaphase, and telophase.

Interphase: is the stage of mitosis where the cell looks like nothing is really happening. In this phase the DNA material is duplicating, but not visible. The nucleus of the cell is still clearly visible and the nuclear membrane has not broken down.

Prophase: During this stage of mitosis the nuclear membrane breaks down and the chromosomes start to move more toward the center of the cell but in a midline arrangement, but they are more like a ball of chromosomes at this point.

Metaphase: During this stage the chromosomes are clearly lined up in a midline formation. In some cases you may see "spindle fibers" attached to the chromosomes and that go toward the pole ends of the cell.

Anaphase: During this stage the chromosomes have begun to moe away from the midline. They are moving toward opposite poles of the cell.

Telophase: During this stage the chromosomes have moved to their respective poles and a pinching of the side walls of the cell may be visible. The nuclear membrane may be starting to form. Soon the original one cell will become two cells.