Cells: Mitosis - Preparing a Root Tip Cell Squash Flashcards
1
Q
Preparing a Root Tip Cell Squash
A
- Add 1M hydrochloric acid to a boiling tube. Put tube in a water bath that reaches 60°C
- Cut 1cm from tip of a growing root (e.g onion)
- Transfer root tip to boiling tube with acid and incubate for 5 minutes
- Remove root tip from tube with tweezers and rinse with cold water using pipette. Leave tip to dry on a paper towel
- Place root tip on microscope slide and cut 2mm from tip
- Use mounted needle to break tip open and spread cells out thinly
- Add few drops of stain and leave for a few minutes
- Place a cover slip over cells and put piece of filter paper on top. Push down to squash the tissue
- Look at all stages of mitosis under an optical microscope
2
Q
Why do we use the tip from a growing root?
A
- It needs to be the tip because that’s where growth occurs and so that’s where mitosis takes place
3
Q
Why do we use stain?
A
- Stain will make the chromosomes easier to see under a microscope
4
Q
Why do we squash the tissue?
A
- Squashing the tissue makes the tissue thinner and allows light to pass through it
5
Q
Using an Optical Microscope
A
- Clip the slide you’ve prepared onto the stage
- Select the lowest-powered objective lens (one that produces the lowest magnification)
- Use the coarse adjustment knob to bring the stage up to just below the objective
- Look down the eyepiece and use coarse adjustment knob to move stage downwards until image is roughly in focus
- Adjust the focus with the fine adjustment knob until you get a clear image of what’s on the slide
- If you need a greater magnification, swap to a higher-powered objective lens and refocus
6
Q
Calculating the Mitotic Index
A
- Mitotic index is the proportion of cells in a tissue sample that are undergoing mitosis
- Mitotic index = Number of cells with visible chromosomes / Total number of cells observed
7
Q
Actual Size Formula
A
- Actual Size = Size of image / Magnification
