An investigator purified a protein (protein X) from E.Coli. Sheinjected protein X into rabbits to generate antibodies thatrecognize and bind to protein X. Using an electrophoretictechnique, she separated the proteins from a crude cell extract andused the antibody to locate protein X on the gel. TO her surprise,the antibody bound not only with protein X but also with a secondunrelated protein (protein Y). When proteins X and Y weresequenced, she found that the sequence of residues 67-78, inprotein X and that of residues 120-131 in protein Y were identical.Help the investigator rationalize the data, recognizing that antigenic determinants (epitopes) of proteins are clusters of aminoacids.