2. The Stages of Cell Division

3. 1. Interphase During Interphase, the cell prepares for division by replicating DNA. The chromosomes are diffuse in their relaxed state.

4. 2. Prophase During Prophase, the chromatin condenses into visible chromosomes. The chromosomes are still dispersed about the cell.

5. 3. Metaphase During Metaphase, the chromosomes line up along the equator of the cell. Spindle fibers attach at the centromeres.

6. 4. Anaphase During Anaphase, the spindle fibers shorten, causing the sister chromatids to separate, and pulling them to opposite sides of the cell.

7. 5. Telophase At Telophase, the spindle fibers disappear. The cell plate forms, separating the cytoplasm as cytokinesis happens.

8. 6. Daughter Cells Finally, you have two cells, each identical to the first cell. These are called daughter cells.

9. In Today’s Lab: WEAR GLOVES FOR ALL STEPS!

10. In today’s Lab, you will be creating wet slides of onion root tips, and then observing the differences between normal onion cells, and those that have been treated with colchicine. In your bin, you have: 2 cups labeled HCl 2 cups labeled Carnoy A dropper bottle of HCl A dropper bottle of Carnoy A slide box with 4 clean slides A container of cover slips 2 forceps A dropper bottle of toluidine blue.

11. Begin by taking the cup marked HCl to the front of the room. Using the forceps, place 3 or 4 onion root tips into the cup. Return to your desk, and add just enough HCl to cover the roots. This will be a very small amount. The most you should add is enough to come up to the line near the bottom of the cup. Allow the root tips to sit for 5 minutes.

12. After the 5 minutes have passed, remove the roots from the HCl and transfer them to the cup labeled Carnoy Add just enough Carnoy to cover the roots. This will be a very small amount. The most you should add is enough to come up to the line near the bottom of the cup. Allow the root tips to sit for 4 minutes.

13. After the 5 minutes have passed, remove a single root from the Carnoy and transfer it to a clean slide. Add one drop of Toluidine Blue. Allow the root tip to sit for 2 minutes.

14. After the 2 minutes have passed, open the top drawer next to your seat and pull out the bibulous paper. Open the book so the page on the left is clean, and place the slide on the right page. Close the book of bibulous, and GENTLY press to blot up the excess dye, without dislodging or squashing the root tip, for a second or so.

15. Carefully open the book of bibulous back up. The excess stain should now be on the left- side page. Remove your slide from the bibulous, and add two drops of distilled water to the root tip. Carefully lay a cover slip over the root tip.

16. Carefully press down on the cover slip with your thumb. Apply enough pressure to flatten the root tip without breaking the slide or the cover slip. The completed squash should look similar to this. Now, observe the cells under the microscope, and fill in the chart in your lab manual. Repeat this procedure again, this time using Colchicine Treated onion roots.

17. Discard used slides in the Glass Disposal Used Carnoy, HCl and root tips go in the Organic Waste Disposal under the fume hood Bibulous paper does not get torn out of the books. Replace the books in the drawers where you found them Clean and put away microscopes. Rinse the cups with water and place them back into the bins for the next class. Anything you removed from the bin should go back into the bin. Clean-up: