Mitosis, also known as karyokinesis, is the process by which the nucleus divides, resulting in two diploid daughter cells. It is the M phase of the cell cycle, which also includes the G1, S, and G2 phases. In G1, the cell grows and performs normal functions. In S, DNA is replicated. In G2, the cell prepares to undergo mitosis. G1, S, and G2 are referred to as interphase-this is where the cell spends the vast majority of its lifespan.
Hypothesis
If observed with the compound microscope, the onion root tip slide should show that the majority of cells are in interphase.
Materials
-Compound microscope
-Onion root tip slide
-Whitefish blastula slide
Methods
We worked in groups of two. After focusing the microscope with the high power objective, we took turns calling out the amount of cells in each stage and recording our numbers (these stages are interphase, prophase, metaphase, anaphase, and telophase). We then calculated and graphed the percentage of cells in each phase.
Statistical test
Consider that it takes 24 hours for onion root tip cells to complete the cell cycle. You can calculate the amount of time spent in each phase of the cell cycle from the percentage of cells in that stage.
Percentage of cells in stage x 1440 minutes = ____ minutes of cell cycle spent in stage
Dependent Variable
The dependent variable was the number of cells in each stage of the cycle in each field of view.
Independent Variable
The independent variable was the field of view observed.
Confounding Variable
We kept the brightness constant throughout the experiment, we made sure that all fields of view were fully occupied every time we counted, and the microscope was undisturbed besides adjustments to focus.
Replication & Sample Size
In the four fields of view we observed, we counted 297 total cells.
Control
There was no control.
Data
The table below shows how many cells were found in each stage in each field of view, the overall percentage of cells made up by each stage, and the amount of time spent in each phase over a 24 hour period.
Data Analysis
The pie chart displays the information in the table found above in graphical format.
As predicted, the majority of the time was spent in interphase.
Conclusion
The hypothesis was supported by our data, as almost three quarters of the cells were in interphase. Unsurprisingly, prophase-the second longest stage- occupied the second largest portion of the chart. This experiment could act as a basis for comparison to other experiments. These onion cells were in arrest; thus, we could perform an experiment using onion cells that have been exposed to a growth hormone and compare the percentages of cells in each of the stages.
Literature Cited
The "AP Biology Lab #3: Mitosis" packet we were provided was used.
No comments:
Post a Comment