GCSE OCR Gateway Biology 1.1 Cell Structure: Students investigate how to extr

Question

Students investigate how to extract DNA from peas.

Stage 1:

- Chill 10 cm³ of ethanol. Keep it on ice throughout the method for use in stage 2.
- Make a thick ‘soup’ by blending 100 cm³ of peas with salt and cold water. Blend for 15 seconds in an electric blender.
- Strain the ‘soup’ through a mesh strainer and collect the liquid part in a beaker.
- Add 30 cm³ of washing-up liquid and swirl to mix.
- Let the mixture settle for 5–10 minutes in a water bath at 60 °C.

a) One group of students made a water bath using a beaker of water, thermometer and Bunsen burner. Another group used an electric water bath.

Write down two advantages of using an electric water bath.

1. ...

2. ...

b) Low temperatures protect DNA by slowing down the activity of enzymes that destroy DNA. High temperatures break down membranes in the cell.

To extract DNA, some methods use a water bath at 60 °C but other methods do not use an increased temperature.

Suggest two reasons for the different methods.

Students investigate how to extract DNA from peas - OCR Gateway - GCSE Biology - Question 16 - 2018 - Paper 1

Worked Solution & Example Answer:Students investigate how to extract DNA from peas - OCR Gateway - GCSE Biology - Question 16 - 2018 - Paper 1

Write down two advantages of using an electric water bath.

Suggest two reasons for the different methods.

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