Fig. 2.

Schematic representation of shifts and nucleotide sequences of cloned products. Chimeric products were amplified with the Mass-D and Ark-U primers covering nucleotide −20 to 580 in the S1 genes. DNA samples were purified with spin columns (Qiagen, Chatsworth, CA) and the DNA was sequenced using the dideoxy method according to instructions (Sequenase Kit, USB, Cleveland, OH) or by the dye terminator cycle method (Ready Reaction, Perkin-Elmer, Foster City, CA) with the Applied Biosystems/Perkin-Elmer automated DNA/RNA sequencer (model 377). Sequences labelled TC (tissue culture) were derived from RNA of co-infected CEK, ECE from RNA of co-infected ECE and C from RNA of co-infected chicks. The sequences of the first 200 nucleotides of S1 genes from recombinants and their parental strains are compared. The sequences of parental strains Mass41 and Ark99 were derived from published data (Binns et al., 1985; Wang et al., 1993).