# Explain why monoclonal antibodies can be used to detect the presence of a specific antigen in a patient's blood sample.

> AQA GCSE Biology (8461) — 4.3.2 Monoclonal antibodies (Bio only) · Explain · 4 marks

> Monoclonal antibodies are widely used in medical diagnosis. They can be used to detect whether a particular antigen is present in a blood sample taken from a patient.

## Mark scheme (4 marks)

1. Monoclonal antibodies are specific to one antigen (complementary to one antigen)
2. The antibody binds to / attaches to the target antigen if it is present in the sample
3. The antibody can be labelled (e.g. with a fluorescent dye / radioactive marker) so that binding can be detected
4. If no binding occurs / label is not detected, the antigen is absent from the sample

## Key terms

- [monoclonal antibodies](https://www.gradenine.co.uk/glossary/monoclonal-antibodies)
- [antigen](https://www.gradenine.co.uk/glossary/antigen)
- [specific](https://www.gradenine.co.uk/glossary/specific)

## Related

- [Revision notes for AQA GCSE Biology (8461)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-monoclonal-antibodies-can-be-8ed17cae) · Published by Druglandscape Ltd.