Final answer:
The experiment on mammalian cell fusion by P.N. Rao in 1970 resulted in the creation of hybrid cells, known as heterokaryones, by fusing cells from different sources. If one original cell was immortal, the hybrid also exhibited immortality and could be maintained indefinitely in culture conditions.
Step-by-step explanation:
The student is asking about the results of the experiment conducted by P.N. Rao on mammalian cell fusion in 1970. In this experiment, the technique employed involved mixing cells from two different sources and exposing them to agents that induced the fusion of these cells to form heterokaryones, which are cells with two nuclei from the original cells.
The fusion of these nuclei could create hybrid cells. In cases where one of the two original cells was immortal and the other was not, the resulting hybrid would also be immortal and could be grown indefinitely in culture. This was a significant step in cellular biology as it allowed for the creation of hybrid cells with unique genetic properties, such as the well-known HeLa cells.