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9th Grade Lab Work. Mitosis in Onion Root Tip Cells
Title: Mitosis in Onion Root Tip Cells
Purpose: to better understand the process and stages of mitosis; to prepare your own specimens of onion root in which you can visualise all of the stages of mitosis.
Equipment: =/=/=/=/=
Background: The stages of mitosis
Prophase. During prophase, the chromosomes supercoil and the fibers of the spindle apparatus begin to form between centrosomes located at the pole of the cells. The nuclear membrane also disintegrates at this time, freeing the chromosomes into the surrounding cytoplasm.
Prometaphase. During prometaphase, some of the fibers attach to the centromere of each pair of sister chromatids and they begin to move toward the center of the cell.
Metaphase. At metaphase the chromosomes have come to rest along the center plane of the cell.
Anaphase. During anaphase, the centromeres split and the sister chromatids begin to migrate toward the opposite poles of the cell.
Telophase. During telophase, the chromosomes at either end of the cell cluster begin to cluster together, which facilitates the formation of a new nuclear membrane. This also is when cytokinesis occurs, leading to two separate cells. One way to identify that telophase has begun is by looking for the formation of the cell plate, the new cell wall forming between the two cells.
Procedure:
- Cut the tip 5 to 8 mm from the tip of the freshly sprouted root. Discard the rest of the root.
- Place the cut tip on a clean microscope slide.
- Cut alongside the root tip.
- Add 2-3 drops of iodine stain to the slide.
- Cover the slide with a cover slip or lens paper.
- Squash the slide with your thumb using a firm and even pressure. (Avoid squashing with such force that the cover slip breaks or slides).
- Observe it under a compound microscope in 10x (200x magnification) objective. Scan and narrow down to a region containing dividing cells and switch to 40x (800x magnification) for a better view.
The root tip should spread out to a diameter about 0.5 – 1 cm.
Attention!!! Record your observations in the table provided.
| Name of the Phase | What I saw under the microscope (with X) |
Result: We carried out all the stages of the lab work correctly.
While conducting part … =/=/=/=/=
1. Find and draw a cell showing each stage of mitosis.
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2. What is a distinguishing visible feature of each stage of mitosis?
Prophase: =/=/=/=/=
Metaphase: =/=/=/=/=
Anaphase: =/=/=/=/=
Telophase: =/=/=/=/=
Conclusion: In part … =/=/=/=/=
In part … =/=/=/=/=
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Point proven.
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