Which of the following accurately describes the core steps involved in a standard Polymerase Chain Reaction (PCR) cycle?

Immunoprecipitation (IP) of protein X from cell lysate using anti-X antibody, followed by RT-PCR for mRNA-Y, indicates the presence of protein X-mRNA-Y complex in vivo. To confirm this interaction, recombinant protein X and in vitro transcribed mRNA-Y are incubated, followed by affinity purification of protein X. However, mRNA-Y was not present in the eluates containing X but rather in the unbound fraction. Given below are a few statements to explain the observations: A. Protein X and mRNA-Y are expressed at the same level in the cell, so the interaction is robust. B. Protein X and mRNA-Y physically interact via a bridge protein/co-factor absent in the purified protein X. C. mRNA-Y binds to the antibody used in the immunoprecipitation. D. The mRNA binding domain of the recombinant protein X may have an altered conformation. Which one of the following is a combination of all correct statements?

Which of the following techniques may be used for identifying a regulatory protein that acts by binding to a specific sequence of DNA?