Nucleotide substitutions during serial passages of the S3 series stocks.

<p>(A) The regions of C ORF containing stop codons introduced in the 4C(-) virus are shown. (B) The electrographs of the region shown in (A) of the S3 series stocks. Appreciable A-to-G (U-to-C) transition substitutions are indicated as arrows, and among these, those causing reversions of introduced stop codons are indicated as stars.</p>