MITOSIS LAB
I. Problem:
Do all phases of the cell cycle (interphase and mitosis) require the same
amount of time? The answer can be found by counting the number of
cells in each stage of mitosis and interphase in a large number of cells in
a tissue. An onion cell takes approximately 24 hours to go through the
entire cell cycle from one to two cells. In this lab, you will find out how
long each step of the cycle takes..
II. Materials:
Prepared slide: onion (Allium) root tip
microscope
Ill. Procedure:
Under high power, identify and count the number of cells in each phase
of mitosis and in interphase. Count the number in the field of vision, then
repeat the process for two other fields.
IV. Data and Results:
A.
Chart your results (data chart example provided)
You can cut this out to use in your resultsData Chart: Onion Root-Tip Mitosis
B.
Calculations for your data chart:.
Percent cells in a phase = number of cells in that phase X 100
total number of cells counted
Assume the number of cells in each phase is directly related to
the time spent in that phase. Onion cells require about 24 hours
(1,440 minutes) to complete the cell cycle from interphase to
interphase. Therefore:
Time for a phase = number of cells in that phase X 1440 min.
total number of cells counted
C.
D.
GRAPH your TIME results in either a Bar Graph or a Circle Graph (pie
chart)
OPTIONAL (ask your teacher) Calculate the CLASS AVERAGE for each
phase time and COMPARE your results to the class results by calculating
% ERROR.
% error = difference between your answer and class answer X 100
class answer
V. Calculations:
Be sure to show ALL calculations for each section of RESULTS!
This includes all formulas and all math written out for part (B) Your
phase time calculations, (D) (optional) Class average calculations,
and % error calculations!
VI. Conclusions:
Thoroughly discuss your findings in this lab. Discussion should
include, but not be limited to:
Based on the Data in your table and graph, what can you infer about the relative
length of time an onion root-tip spends in each stage of cell division?
What stage do cells spend the most time in? Why?
What is the longest MITOTIC phase? What events take place here that might
explain its length?
What is the shortest MITOTIC phase? What events take place here that might
explain its length?