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Edexcel A-Level Biology A2 6.12 Evolutionary Race Between Pathogens and Hosts Questions

Identify the selection pressure on host or pathogen, trace survival and reproduction of the advantageous variant and explain the resulting counter-selection.

Syllabus
First assessment 2019
Course
Biology YBI11
Level
A2

Exam points

  • Explain how new pathogens select advantageous variants in host immune-response genes.
  • Link pathogen mutation to altered antigens and reduced immune recognition or memory response.
  • Apply mutation and selection to antibiotic resistance and the need for new treatments.

Edexcel A-Level Biology A2 6.12 Evolutionary Race Between Pathogens and Hosts Questions question 1

[Maximum number: 2]

Methicillin-resistant Staphylococcus aureus (MRSA) is a disease causing worldwide concerns.

Methicillin is one of the antibiotics to which this pathogen has developed resistance.
Castaneroxy A is a molecule extracted from the European chestnut tree, endemic to Southern Europe and Turkey.

The effects of Castaneroxy A have been investigated.
The investigations have found that Castaneroxy A:
- does not affect the natural skin flora
- prevents MRSA from producing toxins
- weakens the MRSA bacteria
- reduces the size of skin infections caused by MRSA.

Explain why the development of this drug is an example of an 'evolutionary race' between humans and this pathogen.
(2)

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