суббота, 2 февраля 2019 г.

9th Grade Lab. Mitosis in Onion Root Tip Cells

Hey there, everyone. It’s time to do mitosis lab. Here below is a backbone of this lab report. We do the lab with the 9th graders. Use and enjoy!
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.
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.
There are three cellular regions near the tip of an onion root.
1. The root cap contains cells that cover and protect the underlying
growth region as the root pushed through the soil.
2. The region of cell division (or meristem) is where cells are actively dividing but not increasing significantly in size.
3. In the region of cell elongation, cell are increasing in size, but not
The first step will be to ‘soften’ the roots so that they later can be spread on a microscope slide.
1.  Using scissors, cut 2 roots tips about 1 cm long, and transfer them into a plastic micro-tube. (One of the roots will be an extra one.)
2. Fill the tube about 2/3 full with 1N HCl from a dropper bottle. *** Caution: Work with the HCl carefully, it is a strong acid. ***
3. Place the tube in a 60OC water bath, and allow the roots to incubate for 12 minutes.
4. After the 12 minute incubation period, remove the tube from the water bath. 
Rinse the roots in H2O.
1. Using forceps, carefully transfer the root tips to a small plate.
2. Using a plastic ‘squeeze’ pipet, carefully remove the HCl from the micro-tube.
3. Rinse the root tips 3 times with water from the dropper bottle.
Staining the chromosomes.
1. After removing the water from the third rinse, cover the root with the Iodine stain.
2. Incubate the roots in the stain for 2 minutes.
Preparing the root tip squash.
3. Transfer a root to the centre of a clean microscope slide and add a drop of water and IKI.
4. Cover the root tip with a cover slip, and then carefully push down on the cover slide with the thumb. Push hard, but do not twist or push the cover slide sideways. The root tip should spread out to a diameter about 0.5 – 1 cm.
Scan the microscope under the 10x(200x) objective.
Stages of mitosis. Examples are shown.
Since prophase and prometaphase are difficult to distinguish, classify all these cells as prophase. Record your observations in the table provided.
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.

2. What is a distinguishing visible feature of each stage of mitosis?
Conclusion: In part …
In part …

Point proven.

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