DBQ: Use of Monoclonal Antibodies to Diagnose Pregnancy (p.233)
1) Explain how a blue band appears at point C if the woman is pregnant
Pregnancy test kits are available for women to check if they are pregnant or not, through the detection of the hCG hormone. When a women is pregnant, a blue band will appear at point C of the test stick. This is because the increased level of hCG would cause the antibodies that are attached to enzymes bind with the hCG hormone. As the test stick contains monoclonal antibodies, the increased hCG will cause the antibodies to wash down and react to produce the blue color.
2) Explain why a blue band does not appear at point C if the woman is not pregnant
A blue band will not appear at point C if the woman is not pregnant because of the lack of hCG hormone from the urine. Without the hCG, the immobilized monoclonal antibodies cannot bind to the mobile antibodies. Thus, the blue band will not appear.
3) Explain the reasons for the use of immobilized monoclonal antibodies at point D, even though they do not indicate whether a woman is pregnant or not
Point D is where the test strip determines if the test worked correctly or not. The region does not indicate whether a woman is pregnant but still needs to use the immobilized monoclonal antibodies in order to bind with antibodies and produce the blue band, except the hCG is not necessary to produce this reaction.