Fig. 1.
Schema for the derivation of the major lesion in the genome of commonly used AD169 variants from a wild-type virus genome; lengths are shown to scale. In the wild-type genome, the long and short unique sequences (UL and US; shown as thinner structures) are flanked by inverted repeats (ba/b′a′ and ca/c′a′; shown as thicker structures). As indicated by the dashed lines, the AD169 genome was generated by replacing a region at the right end of UL (UL/b′; shaded grey) by an inverted duplication of a region from the left end of the genome (arrow). This resulted in UL becoming shorter by 15 kb (19 genes) and b/b′ becoming longer by 10 kb (six genes and part of another). A similar phenomen occurred in the derivation of the Towne varS genome, with UL becoming shorter by 13 kb (15 genes) and b/b′ becoming longer by 11 kb (seven genes and part of another).