# Explain how viruses that infect bacteria (bacteriophages) are used as vectors in genetic engineering, including the steps by which foreign DNA is introduced into a bacterial host cell.

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

## Mark scheme (4 marks)

1. Foreign DNA / gene of interest is inserted into the bacteriophage genome (in vitro) using restriction enzymes and DNA ligase
2. The recombinant phage is packaged into phage particles (in vitro packaging), producing infective phage vectors
3. The recombinant phage infects the bacterial host cell by injecting its DNA (including the foreign gene) into the bacterium
4. The foreign DNA integrates into / is maintained in the bacterial genome (or as a prophage), allowing expression/replication of the foreign gene in the bacterium

## Key terms

- [bacteriophage](https://www.gradenine.co.uk/glossary/bacteriophage)
- [vector](https://www.gradenine.co.uk/glossary/vector)

## 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-viruses-that-infect-bacteria-275e3d9b) · Published by Druglandscape Ltd.