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?


  Multiple stains are used, each binding to a specific cell structure for easy identification.
• What does acetic orcein stain?


  It 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 does haematoxylin stain?


  It stains RNA/DNA a purple/blue color.
• 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 thinly.
  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.
• Why should the coarse adjustment knob be used first?


  To move the objective lens just above the slide.
• What should you do to focus the microscope?


  Adjust the focus by moving the lens away from the slide using the fine adjustment knob.
• What should be done if a higher magnification is needed?


  Swap to a higher-powered objective lens and refocus.
• How do you measure the size of a structure using a microscope?

  1. Use an eyepiece graticule.
  2. Count the number of eyepiece divisions.
  3. Multiply by the length of one division (calculated during calibration).
• How should drawings made from microscope observations be presented?


  • No shading.
  • Take up at least half of the page.
• What are the guidelines for labeling drawings made from microscope observations?


  • Label lines must be horizontal and drawn with a ruler.
  • Lines must touch the object and not overlap.
  • A scale for magnification should be included.
  • Drawings should be in pencil and resemble the actual image.