Practical questions

You will complete ten required practical activities if you are studying GCSE Biology and twenty-one if you are studying GCSE Combined Science. You could be asked questions about the methods, safety precautions you might take, results and conclusions of these experiments.

These questions have been written by Bitesize consultants as suggestions to the types of questions that may appear in an exam paper.

Sample question 1 - Foundation

Question

In the extraction of DNA it is essential that 90% ethanol is used. Complete a risk assessment for this activity. [3 marks]

HazardRiskControl measure
90% ethanol could act as an irritantInhalation could cause irritation of the nose/throatUse in well-ventilated area/wear safety glasses
90% ethanol could act as an irritantEthanol could touch skin during the experimentUse gloves when pouring ethanol

Sample question 2 - Higher

Question

Describe how you could use the following apparatus to extract DNA from strawberries. [6 marks]

  • re-sealable plastic bag
  • strawberry
  • 10 cm3 washing-up liquid (detergent)
  • 1 g sodium chloride
  • 100 cm3 water
  • 2 × 250 cm3 beakers (one beaker will be used with the filtering apparatus)
  • filter funnel
  • coffee filter paper
  • ice-cold 90% alcohol
  • ice lolly stick or plastic coffee stirrer
  1. Remove the green top from the strawberry.
  2. Put the strawberry into the plastic bag, seal it and crush it for about 2 minutes.
  3. In a beaker, mix together 10 cm3 of washing-up liquid, 1 g of sodium chloride and 100 cm3. This mixture is the DNA extraction liquid.
  4. Add 10 cm3 of the extraction liquid to the bag with the strawberry.
  5. Re-seal the bag and gently mix the extraction liquid with the strawberry for 1 minute.
  6. Place the coffee filter inside the beaker and gently pour the strawberry mixture into it.
  7. Pour 10 cm3 of ice-cold 90% ethanol down the side of the beaker into the strawberry mixture. Do not mix or stir.
  8. Within a few seconds you should see a white cloudy substance form in the clear layer above the strawberry mixture. Use a lolly stick to pull strands of this out of the top layer, this is the strawberry DNA.

Six of these steps correctly described and in the correct order would gain full credit.