Preparing a cheek cell slide

practical

1. Preparing an onion cell slide

2. Aim of this practical To be able to prepare a slide of an onion cell to be viewed under a microscope. To accurately draw observations

3. What you will need… Glass microscope slides Plastic cover slips Paper towels or tissue Iodine solution Plastic pipette or dropper Onion Tweezers

4. Carefully peel back a layer of onion with the tweezers – thinner the better . Place the onion on the slide as flat as possible . Put two drops of iodine on top of the onion ( IODINE STAINS ) . Place the coverslip over the top without bubbles being trapped underneath . Look through microscope at cells. Method

5. Drawing Microscope Slides / Specimens: Use a pencil Draw only the lines you see. No shading or colouring Each circular diagram ( field of view ) should be about a 3 rd of a page in size If the cells you are viewing are similar/repetitive it’s useful to draw about 4-5 only Always record the : magnification name of specimen and the date of the observation

6. Conclusion: What do you see? The iodine solution stains starch in the cells blue-black, making the cell features easier to see.

7. Preparing a cheek cell slide

8. Aim of this practical To be able to prepare a slide of a cheek cell to be viewed under a microscope. To accurately draw observations

9. What you will need… Glass microscope slides Plastic cover slips Paper towels or tissue Methylene Blue solution Plastic pipette or dropper C otton swabs

10. Method Take a clean cotton swab and gently scrape the inside of your mouth. Smear the cotton swab on the centre of the microscope slide for 2 to 3 seconds. Add a drop of methylene blue solution and place a coverslip on top. Remove any excess solution by allowing a paper towel to touch one side of the coverslip. Place the slide on the microscope, with 4x or 10x objective in position and find a cell. Then view at higher magnification

11. Drawing Microscope Slides / Specimens: Use a pencil Draw only the lines you see. No shading or colouring Each circular diagram ( field of view ) should be about a 3 rd of a page in size If the cells you are viewing are similar/repetitive it’s useful to draw about 4-5 only Always record the : magnification name of specimen and the date of the observation

12. Conclusion: What do you see? Methylene blue stains negatively charged molecules in the cell, including DNA and RNA. The cells seen are squamous epithelial cells from the outer epithelial layer of the mouth. The small blue dots are bacteria from our teeth and mouth.