RP 01: Microscopy

Describe how you would prepare a microscope slide for analysis (using onion tissue)

- Peel off epidermal layer using forceps
- Place sample on drop of water on microscope slides
- Add drops of iodine solution to sample
- Lower cover slip onto sample using mounting needle

Why is a thin sample of tissue required?

Allows light to pass through so internal structures can be observed

Why is water added to the slide before the sample is mounted?

Allows the sample to be suspended between the slide and the cover slip, and ensures the cover slip stays in place

Why is iodine solution added to stain the cells?

Iodine solution adds contrast - reacts with starch in plant cells and turns blue-black; allows internal structure (e.g. nucleus) to become more visible

Why is the cover slip lowered using a mounting needle?

Ensures that no air bubbles are trapped

How would you measure the length of a cell viewed under the microscope?

Measure using eyepiece graticule and calibrate with stage micrometer

How would you calculate the magnification of an image?

Magnification = observed cell
length/ actual cell length

What safety precautions should be taken during this experiment?

Wear safety goggles when handling iodine solution