Flashcards · Biology · DNA and Protein Synthesis
Extracting DNA from Fruit
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Why is the fruit mashed?
To break open the cells and cell walls.
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What does detergent do in DNA extraction?
It breaks down the cell membranes and the nuclear membrane, releasing the DNA.
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What is the purpose of salt in the extraction solution?
It helps the DNA to clump together.
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Why is the mixture filtered?
To remove the solid pieces of fruit and cell wall.
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Why is ethanol added?
DNA is insoluble in ethanol, so it comes out of the solution.
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Why is the ethanol ice-cold?
The cold helps the DNA to separate, and slows enzymes that could break it down.
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What does the DNA look like when it appears?
White, stringy strands, like cobwebs.
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Where do the DNA strands appear?
At the boundary between the filtrate and the ethanol layer.
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How can the DNA be removed?
Lifted out with a glass rod or cocktail stick.
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Why are strawberries a good fruit to use?
They have eight copies of each chromosome, so they have a lot of DNA.
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Name one hazard in the experiment.
Ethanol is flammable and harmful.
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How should you add the ethanol?
Slowly, down the side of the tilted tube, so it floats as a layer on top.
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Name one control variable in the experiment.
The mass of fruit, the volumes of solution or the mixing time.
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Is the extracted DNA pure?
No. It also contains proteins and other cell material.
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Why is an experiment like this usually qualitative?
The amount of DNA is hard to measure, so results are mostly descriptions.
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What mistake do students make about the precipitate?
Saying the DNA dissolves in ethanol. It does not, which is why it appears.