Extracting DNA from fruitSpec 3.6
In short
DNA can be extracted from fruit such as strawberries. Mash the fruit, then add detergent, which breaks down cell and nuclear membranes to release the DNA, and salt, which helps the DNA clump together. Filter the mixture, then add ice-cold ethanol on top. DNA is not soluble in cold ethanol, so it appears as white strands.
DNA can be extracted from the cells of fruit such as strawberries or kiwi fruit using simple equipment. Each step has a purpose.
- Mash the fruit in a beaker. This breaks the fruit into small pieces and separates the cells.
- Add a mixture of detergent and salt, and stir. The detergent breaks down the cell membranes (and the nuclear membranes) so the DNA is released. The salt helps the DNA to clump together.
- Filter the mixture. This removes the solid pieces of cell, and the filtrate contains the DNA.
- Carefully add ice-cold ethanol so that it forms a layer on top of the filtrate.
- Look at the boundary between the layers. DNA is not soluble in cold ethanol, so it comes out of solution as white, stringy strands. These can be lifted out with a glass rod.
In a 'why' question, give the purpose of each reagent: detergent breaks down membranes, salt helps the DNA clump together, and ice-cold ethanol makes the DNA come out of solution (precipitate) so it can be seen.
Do not say that you can see the double helix. You see a mass of thousands of DNA strands clumped together.
Quick check
What are the two strands of DNA coiled into?
Show answer
A double helix.
Which bases pair together in DNA?
Show answer
A with T, and C with G.
What is a gene?
Show answer
A section of a DNA molecule that codes for a specific protein.
What is the purpose of the detergent when extracting DNA from fruit?
Show answer
It breaks down the cell membranes to release the DNA.
Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026