DNA Spooling Period 2 and 6

DNA Necklace Kit Student Guide
Instructions
1. Using a marker or label provided by your teacher, write your name or initials on your 15-mL tube.
2. Take the 2 mL of sports drink into your mouth (do not swallow) and swish it around for 1 full minute. As
you swish, gently and continuously scrape the insides of your cheeks with your teeth to help release the
cheek cells.
3. After 1 minute of swishing, spit the sports drink with collected cheek cells back into the small plastic cup.
4. Carefully pour the contents of the small plastic cup into your labeled 15-mL tube. Discard the cup.
5. This is an optional step that will not affect the results of the procedure but allows collected chge): cells to
be seen. You may be instructed to perform this step or to skip ahead to step 6.
If time allows, you can watch your collected cheek cells settle out as a pellet in the bottom of your 15-mL
tube. Place your tube upright in a test tube rack or beaker and let it stand undisturbed. After 5-10
minutes, you will begin to see the cells collect in the bottom of the tube. (Most cells will settle before
30 minutes.) Hold the tube up to the light to better see the cells sinking to the bottom of the tube. Some
collected samples will pellet more tightly and quickly than others, and some will have a higher percentage
of cells than others. This variation is a normal outcome of the procedure.
6. Bring your 15-mL tube to the solution station (if your teacher has one set up). Use a graduated pipet to
add 2 mL of cell lysis solution to your collected cheek cells.
7. Cap your 1S-mL tube tightly and invert it five times. This action mixes the cell lysis solution with the
collected cheek cell sample. Allow the tube to stand for 2 minutes.
8. Bring your 1S-mL tube to the solution station. Hold the tube at an angle and, using a plastic pipet,
carefully add cold 70% ethanol by running it down the inside of the tube. Add the ethanol until the total
volume of liquid reaches 12-13 mL (use the lines on the side of the tube to help you measure). You should
have two distinct layers. Do not mix the cheek cell lysate layer with the ethanol layer.
9. Watch closely as wispy strands of translucent DNA begin to clump together where the ethanol layer meets
the cell lysate layer. The DNA will look like a cobweb extending up from the lysed cheek cell layer. Tiny
bubbles in the ethanol layer will appear where the DNA precipitates.
10. Place your 15-mL tube upright in a test tube rack or beaker and let it stand undisturbed for a minimum of
10 minutes. During this time, DNA will continue to precipitate out of solution and extend like a ribbon
through the ethanol layer. DNA yields from different samples will vary, and not all DNA samples will
extend through the entire ethanol layer.
11. Tie the ends of your embroidery thread together with a knot to form a loop. Make sure the loop can fit
over your head, as this will become your necklace.
12. Use your plastic pipet to transfer your precipitated DNA out of the 15-mL tube and into the pendant tube
(see Figure 1). Begin pipetting the DNA from the end of the most extended strand in the ethanol layer. As
you pipet from this point, the DNA will be drawn up together. You should not move your pipet tip down
into the cell lysate layer. If some of the DNA remains attached to the cell lysate layer, draw your pipet up
until the DNA in your pipet detaches from that in the cell lysate layer. You do not need to transfer the
entire precipitated DNA sample into your pendant tube. Before you expel your DNA into the pendant
tube, allow it to sink to the tip of the pipet so that it will enter the pendant tube first. If the DNA does not
sink, release ethanol into the 15-mL tube dropwise until the DNA is in the pipet tip. Expel the DNA into the
pendant tube and fill the remaining space dropwise with ethanol. Do not overfill.
©2010 Carolina Biological Supply Company/Printed in USA. CARIDLInA S-2