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GCSE Biology · key term
Human chorionic gonadotropin, a hormone that can be detected in urine during pregnancy.
Used by Edexcel
Specification 5.22B · Paper 1
Revise: Monoclonal Antibodies in Pregnancy TestingA pregnancy test does not detect a fetus directly. It detects human chorionic gonadotropin (hCG), a hormone that can be present in urine during pregnancy. Home pregnancy tests are lateral-flow immunoassays: urine moves along a porous strip and antibodies are used to recognise hCG.
For an explanation question, give the whole sequence: hCG in urine binds to labelled monoclonal antibodies; the complexes move along the strip; they bind to immobilised antibodies; the accumulated label forms a coloured test line.
Make it clear that the coloured beads or particles are attached to the mobile antibodies. Do not imply that hCG itself is coloured.
Distinguish the test line from the control line: the test line indicates detected hCG, while the control line shows that the test has operated correctly.
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