Complex sentence: In the 1950s a discovery by two labs simultaneously proved that the purified RNA of the TMV was infectious which reinforced the argument, that had a lot of opposition at the time, that RNA was carrying genetic information to code for the production of new infectious particles.
Split into simpler sentences: In the 1950s a discovery by two labs simultaneously proved that the purified RNA of the TMV was infectious which reinforced the argument. The RNA was carrying genetic information to code for the production of new infectious particles.