Fig. 1.

Genomic structure of the full-length mutant PRRSV cDNA clones. The boxed numbers 1a, 1b, 2a, 2b, and 3 through 7 represented PRRSV open reading frame (ORF) 1a – ORF7. For the mutant PRRSV clones, only the region covering the part of 1b through ORF7 and 3′ UTR is shown. The position and inserted nucleotide sequences are shown. The restriction sites (Pac I, Swa I, Asc I, or Nde I) are underlined and labeled.