Cells in Mitosis
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.
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.
Interphase
• C=
Chromatin
(“spread out DNA” –
chromosomes
not visible yet)
I=
Nucleolus
Prophase
• Chromosomes visible, but unorganized
• A “pile” of visible chromosomes
Metaphase
• Chromosomes lined up in middle of cell
Anaphase
• Chromatids begin to pull apart
Telophase in onion cells
Chromatids reach opposite ends of the cell
Why is the cell not pinched in the middle?
Telophase in food (ha!)
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)
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.