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Practical: Observing Mitosis
Outcome:
In this practical lesson you will prepare samples of onion root tip, a growing part of the onion plant's root system. You will use this sample to observe the different stages of mitosis using a light microscope.
Introduction:
In this experiment you will prepare your own samples of onion/garlic root tip. The root tip is the part of the root system actively growing, as such, it is an excellent source for dividing cells.
You will create your own onion/garlic root tip slides, then observe them under a microscope for mitotic activity.
Vocabulary: mitosis prophase metaphase
anaphase telophase cytokinesis
mitotic spindle microtubules centrioles
chromosomes
Material & Methods
MATERIALS
Spring onion root tips
Ethanol
Methylene blue stain
Microscope
Water at 60 °C
1M Hydrochloric acid (~ 10 mL per working group)
Watch glass (or small dish)
2x 100 mL beaker
Cutting tile
Scalpel
Curved forceps
Microscope slide
Coverslip
Paper towels
METHOD
Cut off 1-2 cm of the spring onion root tips. Put in a small volume of ethanol on a watch glass (or other shallow dish) and soak for 10 minutes.
Meanwhile, heat ~ 10 mL of 1M hydrochloric acid to 60 °C in a water bath.
Wash the root tips in cold water for 4-5 minutes and dry on filter paper.
Use forceps to carefully transfer the spring onion root tips to the hot hydrochloric acid and leave for 2 minutes.
Wash the root tips again in cold water for 4-5 minutes and dry on filter paper.
Use the forceps to remove root tips onto a clean microscope slide.
Use a scalpel to cut each about 2 mm from the growing root tip. Discard the rest, but keep the tips.
Add a small drop of methylene blue stain and leave for 2 minutes.
Break up the tissue with a toothpick.
Cover with a coverslip and place the slide and coverslip on a double layer of paper towel and fold the paper over the coverslip. Make certain that the slide is on a flat surface and squash down on the coverslip with a strong vertical pressure, using your thumb. Do not twist or roll the thumb from side to side.
Observe your sample under a microscope.
RESULTS
RESULTS
Draw diagrams of any mitotic activity you find.
How many cells appear to be dividing?
What phases of mitosis can you see?
Why are the majority of cells not dividing?
Would you expect the garlic/onion epidermis to show similar signs of mitosis?
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