Cell Cycle Lab

Examining Mitosis in the root tip of Allium Already prepared on microscope slides

Objective to observe and identify Interphase, Prophase, Metaphase, Anaphase, and Telophase

Mitosis Phases

Interphase. The cell is engaged in metabolic activity and performing its duty as part of a tissue. The DNA duplicates during interphase to prepare for mitosis (the next four phases that lead up to and include nuclear division). Chromosomes are not clearly discerned in the nucleus, although a dark spot called the nucleolus may be visible.

Prophase. Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nuclear membrane dissolves, marking the beginning of prometaphase. Proteins attach to the centromeres creating the kinetochores. Microtubules attach at the kinetochores and the chromosomes begin moving.

Metaphase. Spindle fibers align the chromosomes along the middle of the cell nucleus. This line is referred to as the metaphase plate. This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one copy of each chromosome.

Anaphase. The paired chromosomes separate at the kinetochores and move to opposite sides of the cell. Motion results from a combination of kinetochore movement along the spindle microtubules and through the physical interaction of polar microtubules.

Telophase. New membranes form around the daughter nuclei while the chromosomes disperse and are no longer visible under the light microscope. Cytokinesis or the partitioning of the cell may also begin during this stage.

Lab

Groups of 2 1 microscope per group 1 microscope slide per group

View slide at 40X Count 100 cells

One group member will observe and one will mark done observations for 50 cells. Then switch and observe remaining 50 cells on a different part of the slide.

1  interphase2  interphase 3  early prophase4  mid prophase5  late prophase6  metaphase7  early anaphase8  anaphase9  early telophase10  telophase 

Microscope Usage

Handle microscope with 2 hands One hand on the base and one hand holding arm of

scope

Focus at 4X first Only time you use course focus (large knob)

Then focus at 10X using fine focus (small knob)

Switch to 40X and focus using fine focus

LabMake table of your small group’s

observations:

Pool class data into table Fill in excel document in class

Interphase 20Prophase 20Metaphase 20Anaphase 20Telophase 20

Observer Observer (Group)(Group)

InterpInterphasehase

PropProphasehase

MetaMetaphasphasee

AnapAnaphasehase

TeloTelophasphasee

ToTotaltal

Group 1Group 1 00Group 2Group 2 00Group 3Group 3 00Group 4Group 4 00Group 5Group 5 00Group 6Group 6 00TOTALTOTAL 00 00 00 00 00 00

Lab Report

Introduction: Background about cell cycle

What are the stages and what is happening in each stage Hypothesis

Relative amount of time spent in each stage

Lab Report

Methods: Prepared slides Count cells/ determine stage Discuss calculations

Lab Report

Results:Include table of class data for each

phase Calculate mean, S.D., and S.E. of CLASS

DATA for each phaseGenerate table of small group resultsInterphase 20

Prophase 20Metaphase 20Anaphase 20Telophase 20

Lab Report

Calculate amount of time cells spent in each stage of mitosis.

Example: Calculate percentage of time spent in a specific stage

from class data Interphase: 756/1200 X 100 = 63%

Use percentage to calculate time spent in stage 16 hours (time it takes to complete cell cycle) x 0.63 = 10.08

hours 0.08 hours x 60 minutes/1 hour = 4.8 minutes 0.8 minutes x 60 seconds/1 minute = 48 seconds Answer = 10 hours 4 mins 48 seconds in interphase

Lab Report

Calculate variability measurement Used to measure variability of class in determination of stages

Higher number indicates more variability Use class data to calculate variability

Calculate for each stage Variability = S.E./Mean

Lab Report

Results Make pie chart of the percentage of time

spent in each stage Use class data for chart

Interphase, 63%Prophase, 15%

Metaphase, 7%

Anaphase, 9%

Telophase, 6%

Lab Report

Discussion Meaning of lab

Why might certain phases take longer, etc. Importance of cell cycle

Lab Report

Conclusion Hypothesis supported? Why/ why not

Lab Report

Introduction ___ Describe cell cycle ___ Discuss cell cycle Methods ___ Counting ___ What the numbers tell us Results ___ Class Data and Calculations (1.5 pts) ___ Individual Data (0.5 pt) ___ Pie Chart ___ Conversion from percent to time Discussion ___ Discuss meaning of the lab Conclusion ___ Hypotheses