Download mitosis lab

MITOSIS LAB
Purpose: Onion root tips are regions of rapid growth, so cells in all phases of the cell cycle can
be observed. The problem to be solved is to figure out how long onion root tip cells spend in
each phase of the cell cycle.
Directions:
1. Examine a prepared onion root tip slide. Using the low power of your microscope, find
an onion root tip.
2. Now, switch your microscope to medium power, and start looking at individual cells.
3. Working with a partner, examine 25 cells in your field of view, and identify the phase of
the cell cycle that each cell is in. Have your partner tally and record in the data table the
phase of each cell you examine. Use pictures below for reference.
cell plate
1 & 2=Interphase
7 & 8=Anaphase
3-5=Prophase
6=Metaphase
9 & 10=Telophase
4. Now switch with your partner. Have your partner move the slide to examine a different
field of view while you tally and record the phases of 25 different cells.
Name _______________________________
MITOSIS LAB ANSWER SHEET
5. Continue in this manner until you have counted 100 total cells together (50/partner).
Interphase Prophase Metaphase Anaphase Telophase
st
# cells in 1
field
# cells in
2nd field
Total each
phase
Fraction of
cells in this
phase
Decimal
% of time
cell spends
in this
phase
# of
degrees in a
circle
graph/phase
6. Add the number of cells in each phase, and record these numbers in the row marked
Total. Total the number of cells you counted and add them up as well.
7. Calculate the fraction of cells in each phase by dividing the number of cells in that phase
by the total number of cells you counted. Express your answer as a decimal, then as a
percentage.
e.g. total cells=100
interphase=80 cells
fraction=80/100
decimal=0.80
percentage= (0.80 x 100)=80%
8. Calculate the number of degrees in a circle graph for each phase by multiplying the
decimal of time the cell spends in each phase by 360degrees. e.g. interphase:
(decimal=0.80) 0.80 x 360 =288 degrees
9. Fill in the circle graph, showing the percentage of time a cell spends in each phase of the
cell cycle. Label each portion of the circle with the phase it represents.
10.Answer the concluding questions.
1. What is the overall goal of Mitosis?
2. In which phase of the cell cycle does a cell spend most of its time? The least time?
3. What are checkpoints and why are they important during the cell cycle?
4. Explain why a slide of stained cells can be used to estimate how much time a living cell
spends in each phase of the cell cycle
5. Describe the appearance of the cell plate in the telophase cells you observed. How would
the division of the cytoplasm appear in an animal cell?
6. An onion cell cycle requires 12 hours for completion (from interphase to interphase).
Using your decimals from each stage, calculate the time (in hours) required for each
phase.
e.g. interphase: 0.80 x 12 hours= 9.6 hrs
Interphase:
Prophase:
Metaphase:
Anaphase:
Telophase: