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3.2 Viral diseases: measles, HIV and TMV

6 exam questions worth 13 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.

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1
Short answer [3 marks]

Describe how measles is spread, and give two of its symptoms.

Mark scheme

  • inhaling droplets (from coughs and sneezes) (1)
  • fever (1)
  • red skin rash (1)

Model answer

Measles is spread when people breathe in droplets from the coughs and sneezes of an infected person. Its symptoms are a fever and a red skin rash.

Your mark
2
Short answer [2 marks]

Give two ways HIV can be spread.

Mark scheme

Any two from:

  • sexual contact (1)
  • exchange of body fluids / blood (1)
  • sharing needles (1)
  • mother to baby (1)

Model answer

HIV is spread by sexual contact and by sharing needles, which exchanges blood.

Your mark
3
Short answer [2 marks]

Explain why people with untreated HIV often die from other infections.

Mark scheme

  • HIV attacks / destroys the immune cells / white blood cells (1)
  • so the body cannot fight other pathogens / infections (AIDS) (1)

Model answer

HIV destroys the immune cells, so the immune system becomes badly damaged and can no longer fight other infections. This is AIDS.

Your mark
4
Extended response [3 marks]

Explain how tobacco mosaic virus reduces the growth of a tomato plant.

Mark scheme

  • discoloured / mosaic leaves with less chlorophyll (1)
  • so less photosynthesis (1)
  • so less glucose for growth (1)

Model answer

TMV causes a mosaic of discoloured patches on the leaves, which contain less chlorophyll. The plant can carry out less photosynthesis, so it makes less glucose and grows less.

Your mark
5
Multiple choice [1 mark]

How is HIV controlled in people who are infected?

Choose one answer.

Correct Not quite: the answer is Antiretroviral drugs

Mark scheme

C

Model answer

C: antiretroviral drugs stop the virus reproducing.

6
Short answer [2 marks]

There is no treatment for measles. Explain why it is important that young children are vaccinated.

Mark scheme

  • measles can be serious / fatal (1)
  • vaccination prevents infection / stops the spread (1)

Model answer

Measles can be fatal and cannot be treated once caught, so vaccinating children stops them getting it and stops it spreading.

Your mark
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