Strawberry DNA
01 // Question
Does a strawberry yield more visible DNA than a fruit with fewer sets of chromosomes, like a banana?
Strawberries are octoploid — each cell carries eight copies of every chromosome, instead of the usual two.
02 // Variables
Independent
Fruit used for extraction- Strawberry
- Banana
Dependent
Amount of visible DNA- Visual scale: none / some / lots
- Notes on strand appearance
03 // Hypothesis
IF strawberries are used instead of bananas for DNA extraction, THEN more visible DNA will float out of solution, BECAUSE strawberry cells are octoploid, carrying eight copies of each chromosome instead of the usual two.
04 // Procedure
1. Mash the fruit
Mash the fruit in a sealed bag with extraction buffer (water, dish soap and a pinch of salt) for 1–2 minutes.
2. Filter it
Pour the mixture through a coffee filter or cheesecloth into a clear tube or cup.
3. Add cold alcohol
Tilt the tube and slowly pour cold rubbing alcohol down the side so it forms a layer on top.
4. Watch the interface
Watch for white, stringy DNA strands rising into the alcohol layer over the next few minutes.
5. Record what you see
Note how much DNA appeared and describe its texture for each fruit.
05 // Data table
| Fruit | DNA visible | Notes |
|---|---|---|
| Strawberry | ____ | ____ |
| Banana | ____ | ____ |
06 // What to expect
Strawberries usually produce a visibly larger, thicker clump of white DNA strands than bananas, because each strawberry cell has eight copies of every chromosome instead of the usual two found in most cells, giving far more DNA per cell to extract.
The soap in the extraction buffer breaks open the cell membranes, and the salt helps DNA strands clump together instead of staying dissolved and invisible in solution.
07 // Lab notes
- Chill the rubbing alcohol in a freezer for at least 30 minutes before the lab — colder alcohol makes DNA clump and become visible faster.
- Pour the alcohol slowly down the tilted side of the tube so it forms a clean layer instead of mixing in.
- Safety. Rubbing alcohol is flammable. Keep it away from any open flame or heat source.
- Safety. Do not taste any part of this lab, even though it uses food ingredients — the soap and alcohol make it unsafe to eat.
08 // Remember
Strawberries have 8 copies of every chromosome. More copies means more DNA to see.
09 // Questions people ask
Why do strawberries work so well for DNA extraction?
Strawberries are octoploid, meaning each cell carries eight copies of every chromosome instead of the usual two found in most plant and animal cells, so there is simply far more DNA packed into each cell to extract and see.
What does the dish soap do in the extraction buffer?
The soap breaks apart the fatty cell membrane and nuclear membrane, releasing the DNA that was packed safely inside the cell and nucleus so it can be filtered out and separated.
Why does the DNA float to the top when alcohol is added?
DNA does not dissolve in cold alcohol the way it does in water, so as the alcohol layer forms on top of the filtered mixture, the DNA strands come out of solution and rise into it, clumping together into visible white strands.