Monoclonal antibodies and ELISAAQA A-Level Biology: Mind map

Exam questions on Monoclonal antibodies and ELISA

1. A hospital is trialling a treatment for a type of breast cancer. A cancer drug is attached to a monoclonal antibody. The antibody binds to a receptor protein that is present in very large numbers on the surface of the tumour cells and in very small numbers on healthy cells.
   Explain why the antibody binds to the tumour cells but not to most healthy cells.2 marks
2. A diagnostic laboratory uses an ELISA test to detect a viral antigen in blood samples. The wells of a plastic plate are coated with the patient's sample so that any antigen sticks to the plastic. A first antibody specific to the viral antigen is then added, followed by a second antibody that carries an enzyme and binds to the first antibody. A colourless substrate is added last.
   A technician forgets to wash the well after adding the second antibody. Explain the effect on the result for a well that contains no viral antigen.2 marks
3. A home pregnancy test detects the hormone hCG in urine. The urine is applied to a pad that contains mobile monoclonal antibodies to hCG attached to blue beads. The liquid flows along a strip past a test line of immobilised monoclonal antibodies to hCG, and then past a control line of immobilised antibodies that bind the mobile antibodies.
   Explain how a blue test line appears when the urine contains hCG.3 marks