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Onion root tip

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					      Creating your own Microscope Slide:
         Mitosis in an Onion Root Tip
Materials: Rooting onions, aceto-orcein stain, HCl, candles and matches,
wood blocks, pipettes, toothpicks, glass slides and cover slips, compound
microscope


                                 Procedure:

Part A: Preparing your slide


1.    Cut 2mm of a fresh onion root tip and place it on the slide.

2.    Place a drop of HCL onto the root tip and wait 1 minute.

3.    Use a toothpick to move the root tip out of the acid. Use lots of paper
      towel to soak up the acid. Throw the paper towel away.

4.    Place a drop of aceto-orcein stain on a slide. CAUTION! If you get
      aceto-orcein on your clothes, it will not come out! If you get it on
      your skin, it will take a long time to come off!

5.    Heat the slide about 3-4 inches over a candle. Move it back and forth
      making sure it DOES NOT BOIL! You want to keep it heated just
      below the boiling point for at least 30 seconds.

6.    Carefully place a cover slip over the stained root tip and cover that
      with a paper towel.

7.    Use a small block of wood or rubber stopper to squash the root tip
      under the cover slip.
Part B: Observing your slide

1.    Place the slide on the microscope and observe it under low power
      (4X).

2.    Look for an area where the cells are almost square and well separated.
      These are the mitotic cells.

3.    Switch the next highest (10X) magnification. Focus in and look for
      the different stages of mitosis.

4.    Now switch to (40X) and focus in.

Record your observations in the boxes provided on the other sheet.

Part C: Prepared Slides

1.    Place the roundworm (Ascaris) or the fish blastula slide on the
      microscope.

2.    Look for at one distinct stage of mitosis. Record your observations
      and write down the stage of mitosis beneath your drawing.

3.    Place the prepared onion root tip (Allium, longitudinal section) under
      the microscope.

4.    Look for another distinct stage of mitosis. Record your observations
      and write down the stage of mitosis beneath your drawing.

				
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posted:8/10/2011
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