microscopy

• What is the purpose of an eyepiece graticule in a microscope?

  It acts like a ruler, allowing structures to be measured under the microscope.
• What is a stage graticule used for?

  It is used to calibrate the value of the eyepiece divisions at different magnifications.
• What are the steps to calibrate an eyepiece graticule?

  1. Set up the microscope to the required magnification.
  2. Place a stage graticule on the stage.
  3. Line up the two scales.
  4. Count the number of divisions on the eyepiece graticule equivalent to each division on the stage micrometer.
  5. Calculate the length of one eyepiece division.
• What must be done if the magnification of the microscope is changed?

  The eyepiece graticule must be re-calibrated.
• What is differential staining?

  • Use of multiple stains
  • Each stain binds to a specific cell structure
  • Structures can be easily identified
• What does acetic orcein stain?

  It binds to DNA and stains chromosomes dark red.
• What color does eosin stain cytoplasm?

  Dark red or pink.
• What color does iodine stain starch?

  Blue-black (appears violet under the microscope).
• What color does iodine in potassium iodide solution stain cellulose?

  Yellow.
• What color does haematoxylin stain RNA/DNA?

  Purple/blue.
• What is methylene blue used for?

  It is an all-purpose stain, often used to stain DNA blue.
• What are the steps for preparing a wet mount slide?

  1. Use a pipette to put a drop of water on the slide.
  2. Place the specimen in the water using tweezers.
  3. Add a cover slip carefully to avoid bubbles.
  4. Add a stain using a drop on one edge and a paper towel on the opposite edge.
• What are the steps for preparing a dry mount slide?

  1. Slice the specimen into a thin piece.
  2. Use tweezers to place it in the middle of the slide.
  3. Put a cover slip on top.
• What is the first step in using a light microscope?

  Clip the slide onto the stage.
• What should be done after selecting the lowest-powered objective lens?

  Use the coarse adjustment knob to move the objective lens just above the slide.
• How should focus be adjusted when using a light microscope?

  By moving the lens away from the slide using the fine adjustment knob until a clear image appears.
• What should be done if a higher magnification is needed?

  Swap to a higher-powered objective lens and refocus.
• How is size measured with a microscope?

  • Use an eyepiece graticule.
  • Count the number of eyepiece divisions.
  • Multiply by the length of one division (calculated during calibration).
• How should the diameter of an irregularly shaped object be measured?

  By measuring the greatest distance from one side to the other.
• What are the guidelines for drawing microscope images?

  • No shading; label shaded areas.
  • Drawing should take up at least half of the page.
  • Label lines must be horizontal and not overlap.
  • Drawing lines should connect completely and not be hairy.
  • A scale for magnification should be included.
  • Drawings should be in pencil and resemble the actual image.