# Pregnancy testing kits use monoclonal antibodies to detect the hormone hCG in urine. Explain how monoclonal antibodies make this test specific to hCG and describe what happens in the test when hCG is present.

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

> Pregnancy testing kits contain monoclonal antibodies that are specific to the hormone human chorionic gonadotropin (hCG), which is only present in the urine of pregnant women.

## Mark scheme (4 marks)

1. Monoclonal antibodies have a specific shape / binding site complementary to hCG (antigen)
2. So they will only bind to / attach to hCG and not other substances / antigens
3. When hCG is present, it binds to the monoclonal antibodies on/in the test strip
4. This causes a visible colour change / line to appear, indicating a positive result

## Key terms

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

## 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/pregnancy-testing-kits-use-monoclonal-antibodies-c579c316) · Published by Druglandscape Ltd.