A pregnancy test has a test line and a control line. The control line appears when labelled antibodies have moved along the strip correctly, whether hCG is present or absent.
After urine is added, neither line appears.
Which conclusion is justified?
The test is negative because the control line appears only when hCG is present.
The test is invalid because correct movement along the strip has not been confirmed.
The test is positive because hCG prevents labelled antibodies moving along the test strip.
The test is negative because absence of both lines confirms that hCG is absent.
45 exam-style questions on Edexcel GCSE Biology 5.3 Immune system and medicines, covering 5.3.1 The specific immune system, 5.3.2 Response to immunisation, 5.3.3 Advantages and disadvantages of immunisation, 5.3.4 Antibiotics and bacterial infections, 5.3.5 Aseptic techniques in culturing, 5.3.6 Cross-sectional areas of cultures, 5.3.7 Stages of developing new medicines, and 5.3.8 Production of monoclonal antibodies. Each one has a worked solution and a mark scheme showing where the marks go.