# Explain how a retrovirus such as HIV integrates its genetic material into the host cell genome and discuss the consequences of this integration for the host cell.

> IB DP Biology Higher Level (2023 syllabus) — A2.3 Viruses (HL only) · Explain · 4 marks

## Mark scheme (4 marks)

1. HIV carries reverse transcriptase, which transcribes the viral RNA genome into DNA (reverse transcription).
2. The viral DNA is transported into the nucleus and integrates into the host cell's chromosomal DNA using the viral enzyme integrase, forming a provirus.
3. The provirus may remain latent (dormant) within the host cell, meaning the infection is not immediately cleared by the immune system / antiretroviral drugs cannot eliminate latent reservoirs.
4. When the provirus is activated, host cell transcription machinery transcribes the viral genes, leading to production of new virions / the host cell may be destroyed or, if integration disrupts a tumour-suppressor gene or activates an oncogene, may lead to malignant transformation.

## Key terms

- [retrovirus](https://www.gradenine.co.uk/glossary/retrovirus)
- [integration](https://www.gradenine.co.uk/glossary/integration)

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](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-how-a-retrovirus-such-as-4a2c4be9) · Published by Druglandscape Ltd.