This document provides instructions for an experiment to extract DNA from a banana. Students will mash a banana, mix it with saltwater and detergent, then pour the mixture through a coffee filter. Rubbing alcohol will then be slowly added to form separate layers, with the DNA visible as a cloudy substance between the layers. After 8 minutes, a wooden stirrer can be used to remove strings of DNA from the mixture. The experiment demonstrates that all living things contain DNA and how different materials are used to isolate it from banana cells.

1. FIND THE DNA IN A BANANA
LAB PRACTICE
EIGHTH GRADE
Guided Stage.
LAB REPORT
1. Tittle: Find the DNA in a banana.
2. Objectives:
• Identify the lab practices as axis of work in the biology
• Observe the DNA material in a banana and analyze its structure.
• Consolidate the knowledges with a lab practice.
3. Theory:
4. Hypothesis: a prediction about the experiment, which will be the result.
5. Equipment, instruments and materials used: Description, function and drawing of each one.
6. Procedure.
7. Data and information.
8. Calculations and results.
9. Analysis.
10. Conclusions.
11. References.
MATERIALS
1. Ripe banana
2. Half cup of water
3. Teaspoon of salt
4. Resealable zip-top bag
5. Dishwashing soap or detergent
6. Rubbing alcohol
7. Coffee filter
8. Narrow glass

2. 9. Narrow wooden stirrer
PREPARATION
1. Place your bottle of rubbing alcohol into the refrigerator or freezer and let it chill for the
duration of this experiment.
2. Peel a banana.
3. Put the peeled banana in a resealable zip-top bag and close the bag.
4. On a hard surface like a tabletop or kitchen counter, mush the banana in the bag for about a
minute until it has a fine, puddinglike consistency and until all lumps are gone. Do not slap the
bag or mash the banana too close to the bag's zip seal. (This could cause the seal to open and the
banana to squirt out and make a mess.)
PROCEDURE
1. Fill a measuring cup with a half cup of hot water and a teaspoon of salt.
2. Pour this saltwater into the bag, and close the bag. Gently mix and slosh the saltwater and
mashed banana together for 30 to 45 seconds.
3. Add a half of a teaspoon of dishwashing detergent or dish soap into the bag. Again, mix around
the contents gently. You do not want the mixture to become too foamy.
4. Place the bottom half of a coffee filter in a clear glass cup. The top part of the filter should be
folded over the rim of the glass to keep it in place.
5. Carefully pour the contents of the bag into the filter and let it sit for several minutes until all of
the liquid has dripped down into the cup. (You can now throw out the coffee filter and its
contents.)
6. Take the rubbing alcohol from the refrigerator. Tilt the glass and slowly pour the alcohol down
the side of the cup until there is a layer that is 2.5 to five centimeters (one to two inches) thick.
You want to keep the alcohol and the liquefied banana as separate as possible, so complete this
step slowly.
7. Let this two-layered mixture sit for eight minutes. During this time, what do you see happening
between the alcohol and the banana liquid layer? It looks cloudy and may have some tiny

3. bubbles in it. The longer you wait, the more defined this layer becomes. This is the DNA pieces
clumping together.
8. Stick the wooden stirrer into the cup. Spin it in place so that cloudy layer spools around it.
Remove the stirrer. Can you capture some of the stringy middle layer on your stirrer and remove
it from the cup? The substance that you see on the stirrer is DNA!
OBSERVATIONS AND RESULTS
The stringy substance that you see is DNA! It has been removed from the millions and millions of cells
that make up the banana. All living things have DNA. The more similar and closely related two living
things are, the more similar their DNA is. Every human shares 99 percent of his or her DNA with every
other person. Furthermore, human DNA is very similar to that of other species. We share most of our
genes, which make up DNA, with fellow primates such as chimpanzees and with other mammals such as
mice. We even have genes in common with the banana plant!
In this activity each material plays a specific role in helping to extract the DNA from the cells. For
instance, the detergent or soap helps to break down the cell's outer membrane, and the salt helps to
separate the DNA from other materials in the cell. And because the DNA doesn't dissolve in alcohol, this
substance helps the DNA clump together in a separate layer
From: https://www.scientificamerican.com/article/find-the-dna-in-a-banana-bring-science-home/