Coding region has no apparent effect but CMV promoter orientation has a significant effect on induction of swelling. (A) Viruses D, E, and F contain the CMV promoter in the rightward orientation. The numbers of ears analyzed were: virus D, 18; virus E, 12; virus F, 6. (B) Viruses G-J contain the CMV promoter in the leftward (anti-E1A) orientation. The numbers of ears analyzed were: virus F, 9; virus G, 6; virus H, 18; virus I, 12.