Award 0 to 3 points by placing a check in the appropriate box based upon the information below.

If the student has:

• used the lower onion epidermis tissue - 1 point
• used a piece of tissue that is smaller in size than the cover slip - 1 point
• not folded or damaged the specimen in preparing the wet mount - 1 point

Award zero points if none of the above are met. Place a dash (--) in each box to indicate that no points were given.

Award 0 to 2 points for the amount of liquid used in preparing the wet mount slide by checking the appropriate box based upon the following:

• if sufficient water was used - 1 to 2 points

If too little or too much water was used, award zero points by placing a dash (--) in each box to indicate that no points were given.

Award 0-3 points for the occurrence of air bubbles visible to the unaided eye by checking the appropriate box based upon the following.:

• no air bubbles visible - 3 points
• few small air bubbles visible - 2 points
• many small or one large air bubble visible - 1 point

If more than one large air bubble is visible to the unaided eye, award zero points by placing a dash (--) in each box to indicate that no points were given.

PROCEDURE B

1. Student identifies slide number - non scored.
   
   
2. Focusing under low power:
   
   

   

   Point Range Code Values:

   D -- 0
   E -- 1
   F -- 2

   Award 0-2 points for low power focusing by checking the appropriate box based upon the following:

   • image in sharp focus - 2 points
   • image out-of-focus - 1 point
   • image not visible - 0 points
     
     

3. Identify the colored thread that is on top of the others and write it on the line below:
   

   ___________________________________
   
   

   

Point Range Code Values:

G -- 0
H -- 1

Award 0-1 points for identifying the correct color thread by checking the appropriate box based upon the following:

• correct color thread identified - 1 point
• incorrect color thread identified - 0 points

Award 0-2 points for high power focusing by checking the appropriate box based upon the following:

• image in sharp focus - 2 points
• image out-of-focus - 1 point
• image not visible - 0 points

PROCEDURE D

Before scoring this section, it is necessary to compile information about the microscopes and prepared slides of the onion epidermis that will be used in the testing. Follow the steps below to determine the microscope low and high power field of view diameters, average onion cell length, and approximate nucleus diameter.

1. Determine the diameter of the 100x field of view for the microscope(s) used in the skills test.
   
   NOTE: Repeat the data below if microscopes are of different manufacturers, models, or have different oculars or objective lenses.

   100x field of view diameter in millimeters: ________________

   Convert to micrometers: 1 millimeter = 1000 micrometers

   100x field of view diameter in micrometers: _________________

2. Prior to the testing, examine each prepared slide of onion cells to be used to determine the average number of cells end to end that span the diameter of the field of view. Code each slide to identify differences in the onion epidermis tissue used to manufacture the prepared slide. Record the information below:
   

   Slide No: __________ Number of onion cells end to end: __________

   Slide No: __________ Number of onion cells end to end: __________

   Determine the average onion cell length in micrometers using the following:

   

   Slide No: __________ Average length of a single onion cell: ___________

   Slide No: __________ Average length of a single onion cell: ___________

3. Determine the diameter of the high power field of view for each microscope by using the following:
   

   

   High power field of view diameter in micrometers: ____________

   High power field of view diameter in micrometers: ____________

4. Examine an onion cell on the prepared slide and determine the approximate diameter of its nucleus in micrometers by comparing it to the average cell length. Use the following information:
   

   

Scoring:

Item:

2. If the student correctly measures the field of view diameter +/-.25 millimeters, award 1 point.
   
   
3. If the student correctly calculates the field of view diameter based on the above measurement in micrometers, award 1 point.
   
   
4. If the student correctly explains and/or shows how the average length of an onion cell is calculated based upon the information in D above, award 1 point.
   
   

   If the student correctly calculates the length of a single onion cell, award 1 point.

5. Non-scored item.
   
   
6. If the student correctly explains and/or shows how the diameter of the high power field is calculated based upon the information in C above, award 1 point.
   

   If the student correctly calculates the diameter of the high power field, award 1 point.

7. If the student correctly explains and/or shows how the approximate diameter of a single onion cell nucleus is calculated based upon the information in D above, award 1 point.
   
   

   If the student correctly calculates the approximate diameter of a single onion cell nucleus, award 1 point.

SUMMARY SCORING SHEET

Maximum points for each item are identified in parentheses.