Name ____________________________________________________________
The Onion’s Tip
(from the Biology Project, University of Arizona)
In this activity, you will be presented with cells from the tip of an onion root. Using your notes,
you will classify each cell based on what phase it is in. At the end you will count up the cells
found in each phase and use those numbers to predict how much time a dividing cell spends in
each phase. You can base your calculation on a total cell cycle of 24 hours.
Enter data in this table below.
Interphase Prophase
Metaphase Anaphase
Telophase
Total
Number of
Cells
36
Percent of
Cells
100%
Examples of pictures of cells in each phase:
Interphase - In interphase, the chromosomes are not condensed yet, and individual
chromosomes cannot be distinguished.
Prophase – Chromosomes in prophase are visible, but are not organized.
Metaphase – Cells in metaphase have distinct chromosomes that are lined up along the middle of
the cell.
Anaphase – In anaphase, the sister chromatids separate and migrate to opposite poles of the
cell.
Telophase – In telophase, the sister chromatids have been pulled to opposite sides of the cell
and the nuclear membrane forms around each new nucleus.
Interphase
Prophase
Metaphase
Anaphase
Telophase
Identify which phase the cell is in the pictures below:
Phase
Phase
Phase
Phase
Phase
Phase
Phase
Phase
Prophase (spindle)
Telophase
Telophase (chromosome/ centromere)
Interphase
Metaphase (spindle fiber)
Anaphase
Telophase
Interphase (nuclear membrane, nucleolus, and centriole)
Phase
Color
Anaphase – the phase of mitosis in which the chromosomes begin to separate.
Centrioles – paired cylindrical organelles, arranged at right angles to each other, located at the
center of a microtubule.
Centromeres - a centromere is the constricted region of a nuclear chromosome - microfibers
attach to the centromere during mitosis.
Chromosomes - structures in the nucleus that contain DNA molecules that contain the genes.
Interphase - the phase of a cell's life cycle in which DNA is replicated.
Microtubules - tiny filaments (about 25 nanometers in diameter) that are active in mitosis.
Metaphase - the phase of mitosis in which the chromosomes line up at the equator (the central
plane) of the cell.
Prophase - the phase of mitosis in which the duplicated chromosomes condense, the nuclear
envelope dissolves, and centrioles divide and move to opposite ends of the cell.
Telophase - the last phase of mitosis, when the chromosomes migrate to opposite ends of the
cell, two new nuclear envelopes form, and the chromosomes uncoil.
Name _______________________________________________ Score ________
The Magic Universe of Cells: How Many Cells are Born in a Day?
Materials

Calculator
Safety Concerns: None
Procedure
Your cell divides every hour. Assuming no cells die during the 12-hour period, how many
cells will exist after each hour? How many cells would exist after 12 hours? After you
use the chart below as a worksheet, graph your results on the back of this sheet of
paper. One axis of the graph should represent the number of cells and the other axis
should represent the hours up to the 12th hour.
Cell Division Chart
Hour
1
2
Number of Cells
3
4
5
6
7
8
9
10
11
12
Look at your graph. What pattern do you notice?