1A. Image of an amoeba shortly after transplant of a labeled nucleus (arrow). 1B. Autoradiograph image of the amoeba shown in 1A. Radioactivity appears in black, and is confined to the nucleus ...

enucleated amoeba. They reasoned that if RNA originated in the nucleus, radioactivity would, at the end of the experiment, be detected in both nucleus and cytoplasm. In contrast, if RNA did not ...