(5 pts total, variable points) A tumor biopsy is prepared fo…

(5 pts total, variable points) A tumor biopsy is prepared for immunohistochemistry (IHC) to assess Ki-67, a nuclear protein expressed during cell proliferation. The tissue is fixed, sectioned, and incubated with a rabbit anti–Ki-67 primary antibody. After washing, a goat anti-rabbit IgG secondary antibody conjugated to alkaline phosphatase (AP) is applied. When the chromogenic substrate Fast Red is added, red staining appears in the nuclei of dividing cells. A. (1 pt) What molecule is acting as the antigen in this experiment?  B. (2 pts) What are the specific roles of the primary antibody and the secondary antibody in IHC detection? C. (2 pts) Which is the binding protein(s) and which is the enzymatic protein(s)?