The mitosis of onion root tips involves the process of cell division in its various phases, such as interphase, prophase, anaphase, metaphase and telophase. In biology labs, students use onion root tips to observe these different phases of a cell cycle. Placing a stained slice of a root tip under a light microscope facilitates the viewing of the large chromosomes, which appear dark due to staining.
During interphase, DNA duplication occurs in preparation for the start of mitosis. At this stage, chromosomes may not be visible in the nucleus, but the nucleolus is viewed as a dark spot under a microscope. In the prophase stage, condensing chromosomes are visible, and the attachment of spindle fibers to chromosomes is observable in metaphase. During anaphase, students can see pairs of chromosomes.
The last stage of the cell division of an onion root tip is telophase. In this phase, the separation of the paired chromosomes occurs, and they move to opposite sides of the cell. Cytokinesis, which is the division of the cytoplasm, can occur in late telophase.