1. Cells in Mitosis

2. Mitosis in Onion Cells!
You will be examining onion root tip cells. These cells are used because the root tip is growing.
In order for tissue to grow, cells must either:
1) get larger, or
2) divide to form new cells (cell cycle and mitosis)
These root tips have hundreds of cells growing and dividing (undergoing mitosis).
Note: if mitosis goes badly (chromosomes don’t line up or separate appropriately), the new cells probably won’t survive.

3. Onion root tip cells under high power
A few cells
dividing
Lots of cell dividing
Your field of view should look similar to these! If they don’t, look at another part of the root tip.

4. Interphase C = I = Chromatin Nucleolus (“spread out DNA” – chromosomes
not visible yet)

5. Prophase Chromosomes visible, but unorganized
A “pile” of visible chromosomes

6. Metaphase
Chromosomes lined up in middle of cell

7. Anaphase
Chromatids begin to pull apart

8. Telophase in onion cells
Chromatids reach opposite ends of the cell Why is the cell not pinched in the middle? Telophase in food (ha!)

9. Instructions:
Choose who will read directions (you or your partner). No sign in.
Onion slides are either with me or on your microscope stage.
No books! Just notes.
Part I: Draw 5 cells in different phases of mitosis and describe them!
Note: one entire cell should fill a box on your handout.
DRAW WHAT YOU SEE, not what you THINK you should see.
If you are not sure which phase a cell is, give your best guess – or ask Mr. Welman for help! You may use your Cornell notes, too
You will NOT see spindles/centrioles. Don’t draw them.
I will only stamp part II if your drawings are accurate and awesome in part I. Take your time. You have tomorrow, too.
It can be challenging to find some phases (e.g. metaphase). Be patient, keep looking.
In Part I you must show me one phase (not Interphase)

10. Day 2
Part I: Finish what you started yesterday – find and draw 5 phases
Get a stamp after Part 2
Show me one identified cell – NOT interphase – from Part 1
I will only stamp if drawings are accurate and excellent. Take your time.
Part II: Scan 25 additional cells, determine what phase each one is in, and record this data. Get a stamp after you have completed this.
4 interphase
2 prophase
1 anaphase
(do this for 25 cells…)
If you finish early, work on homework. Books available on the cart. Your answers must clearly be your own.