# Explain why the development of antibiotic-resistant bacteria is a serious problem for treating bacterial infections, and describe how antibiotic resistance develops in a bacterial population.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 5.4 Antibiotics and resistance · Explain · 5 marks

> Antibiotic resistance is an increasing global health concern. Some strains of bacteria, such as MRSA, can no longer be killed by many commonly used antibiotics.

## Mark scheme (5 marks)

1. Antibiotics kill or prevent the growth of bacteria / antibiotics cannot kill antibiotic-resistant bacteria
2. Random mutation(s) occur in the DNA of some bacteria
3. Resistant bacteria survive and reproduce when antibiotic is present / non-resistant bacteria are killed by the antibiotic
4. Resistant bacteria reproduce and pass on the resistance gene / resistant allele to offspring (natural selection)
5. Over time the proportion of resistant bacteria in the population increases, making infections harder to treat / existing antibiotics become ineffective

## Key terms

- [antibiotic](https://www.gradenine.co.uk/glossary/antibiotic)
- [antibiotic resistance](https://www.gradenine.co.uk/glossary/antibiotic-resistance)
- [bacteria](https://www.gradenine.co.uk/glossary/bacteria)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-the-development-of-antibiotic-resistant-f62ffd96) · Published by Druglandscape Ltd.