Download DNA Extraction Lab dna_extraction_protocol_dnai_2011

DNA EXTRACTIONS
Background
One important characteristic of living things is that their cells contain DNA. It doesn’t matter if
you are human, dog, bacteria, mushroom, or strawberry – all living cells contain DNA. In this
lab you will extract the DNA from a strawberry or kiwi fruit. You will attempt to then ‘spool’
the extracted DNA on a glass rod.
Learning Objectives
 Students will be able to construct a detailed flow chart of a laboratory procedure.
 Students will be able to follow their lab flow chart to successfully extract and spool DNA
from fruit.
 Students will analyze the purpose of various steps of the DNA extraction.
Materials
 Heavy Duty Ziplock
 Strawberry or ½ kiwi fruit
 30 mL detergent-salt solution
 1 mL pineapple juice (natural enzyme)
 filter and funnel
 test tube
 beaker
 Rubber band
 graduated cylinder
 glass stirring rod
 Ice cold ethanol
Protocol
1. Place the 1-2 strawberries (or equivalent amount of other fruit) into a ziplock bag and crush
for about 1-2 minutes. Note: you may remove stem and leaves
2. Add 30 ml of the soap detergent solution into the bag.
3. Crush and mash again until the solution is smooth.
4. Add 1 ml of pineapple juice to the bag.
5. Mix gently for 1 minute—just get the pineapple juice (containing natural enzymes) evenly
distributed.
6. Gently pour the solution through filter into a beaker.
7. Funnel 6 ml of the filtrate (filtered liquid) in the test tube.
8. Get 6mL ethanol from the class supply (at the teacher’s lab station)
9. Carefully pour the ethanol down side of test tube. You want to pour the ethanol so that it
forms a layer on the top of the filtrate.
10.Wait 1-2 minutes – You should see DNA rising out of the filtrate. During this time,
complete a drawing of your test tube on next page.
11.Spool the DNA (pick up DNA on the glass rod by circling the stir stick very slowly in the
DNA such that it adheres to the stir stick).
Pre-lab Flow Chart
Prior to lab, construct a step by step flow chart of the procedure you will use for the lab. Use
pictures and words for each step of the lab. Doing this well will help you process what the steps
of the lab are prior to actually conducting the lab. Your goal is to be able to follow your flow
chart directly without needing to refer to the written procedure in order to complete your lab.
NOTE: YOU MAY NOT MOVE TO THE LAB STATION UNTIL YOUR PROTOCOL
DRAWINGS ARE COMPLETE AND CHECKED OFF BY YOUR TEACHER!!!!
Results
Draw a picture of what the tube looks like prior to spooling the DNA. Label supernatant
(liquid), ethanol, and DNA.
After spooling, provide additional observations of the DNA (i.e. general appearance, texture,
consistency, etc.).
Analysis Questions
For help in answering analysis questions, go to the following website.
(http://learn.genetics.utah.edu/content/labs/extraction/howto/). Be sure to click on the links
that explain why certain steps are performed in your DNA extraction.
1. The DNA in a cell can be found in the nucleus. Recall from cell biology that both the
membrane around the cell and the membrane around the nucleus are made up of lipids.
(Remember that lipids = fats= oils). What step in the lab protocol do you think is
responsible for breaking down the cell and nuclear membranes? Explain your answer.
2. Pineapple juice is a natural enzyme. Enzymes are special proteins that make processes
occur, or makes them occur faster. Explain the role/ function this enzyme played in the
DNA extraction lab?
3. Explain the role ethanol (alcohol) played in extracting the DNA. (Hint, what happened
when you added the ethanol to your test tube?)
4. DNA extractions from strawberries provide a large amount of DNA because they have an
excess of DNA. Provide 3 examples of other items (besides fruit) we could have used
for this lab.
5. Explain the basic function of DNA for any living organism.