Answer:
The change of color in the sample wells with the color in a known sample
Step-by-step explanation:
Enzyme-linked immunosorbent assay (ELISA) is a technique widely used in molecular biology laboratories to measure antibodies, antigens and/or proteins in the samples that are being analyzed. This assay uses antibodies and color changes in order to identify target substances. The ELISA assay is heterogeneous because the antibody or the antigen is immobilized in a solid support composed by wells of microtiter plates. This assay uses chromogenic reporters and substrates that produce color changes, thus evidencing the presence of antigens which can be species-specific.