“…In addition to sequence comparisons to determine important areas within the genome, studies using infectious complementary DNA clones have become very powerful. Infectious transcripts for different picornaviruses have been prepared: polioviruses (Racaniello and Baltimore, 1981;Omata et al, 1984;Kaplan et al, 1985), human rhinovirus type 14 (Mizutani and Colonno, 19851, coxsackie B3 virus (Kandolf and Hofschneider, 1985), EMCV (Naviaux et al, 19901, hepa-titis A (Cohen et al, 1987), and foot-and-mouth disease virus (Zibert et al, 1990). Infectious transcripts for members of both TMEV subgroups DA (Roos et al, 1989131, BeAn (Calenoff et al, 1990), and the highly virulent GDVII (Tangy et al, 1989) have been constructed.…”