Observation of the Mitotic Cell Cycle in Onion RootsINTRODUCTIONThe cell cycle refers to the sequence of events that takes place in a cell leading to its division and duplication (replication). This process is important for genetics because through the cell cycle genetic information for all types is passed from parents to daughter cells. (Griffiths. A et al)A new cell begins after dividing and producing two new cells. Each new cell undergoes metabolism, growth and development. At the end of its cycle the cell divides and produces two new cells which then undergo a further cell cycle. (Elseth .G et al) The cell cycle consists of two main phases: the first is interphase (a prolonged period of cell growth, in which the nutrients necessary for mitosis accumulate and DNA is synthesized). The second period is the mitosis phase (M phase) during which the cell divides into two distinct cells called daughter cells. (Griffiths. A et al) Mitosis is divided into four phases: prophase, metaphase, anaphase and telophase. When the living organism needs new cells to repair damage, grow, or maintain its condition, the cells undergo the cell cycle. The cell cycle is a significant process by which the single-celled fertilized egg develops into mature organisms, as well as the process by which hair, blood cells, and some internal organs are renewed (Practical Biology.org). Purpose: The scientific purpose of this study is to observe the phases of cell cycles in living tissues, generally and specifically in the meristematic cells of the onion or garlic root, and calculate the percent mitotic index.METHOD1-2 mm growing root tip the garlic roots were cut. The root tip was placed in one of the Petri dishes and a few drops of 1 M hydrochloric acid... in the center of the paper... without overlapping the cells. We also used toluidine blue to stain the samples so that the chromosomes can be observed clearly and finally in the experiment, the coverslip was used to flatten the root tip of the onion for better visualization. In conclusion, the cell cycle can be divided into interphase and M phase (mitotic phase). The interphase can be divided into three different phases; they are the G1 phase (first gap), the S phase (synthesis) and the G2 phase (second gap). The M phase consists of mitosis and cytokinesis. Mitosis, on the other hand, consists of four main phases which are prophase, metaphase, anaphase and telophase. The most important phase of the cell cycle is interphase, followed by prophase. The shortest would be metaphase, anaphase, and telophase. The higher the percentage of cells, the longer each cell spends in that phase. Therefore the hypothesis is accepted.