Timing of the Cell Cycle The cell cycle takes various lengths of time to complete depending on the type of cell. An onion root tip preparation can be thought of as a snapshot capturing cells in various phases of the cell cycle at a particular moment in time. The frequency of occurrence of a cell cycle phase is directly proportional to the length of a phase. You can therefore estimate the amount of time each phase takes by tallying the proportions of cells in each phase. The length of the cell cycle for cells in actively dividing onion root tips is approximately 24 hours, with mitosis lasting for about 90 minutes.
Identify and record the phase that each of 100 cells is in. This is done fairly easily by getting an onion root photo with at least 10 columns of cells and record the phase of each cell while scanning down several rows of cells, one cell at a time. Record the number and phases of the 100 cells in the table below.
Phase Number Seen (Tally 96 Of Total Number Duration of Phase
marks) of Cells (Proportion of 24 hours)
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total
Which phase of the cell cycle had the highest percentage of observations?