( A ) PCR amplification of the env gene from DF-1/K cells. (M) DNA marker; (DF-1/K): Genomic DNA extracted from DF-1/K cells; (DF-1): Genomic DNA extracted from DF-1 cells. ( B ) Verification of the stability of the ALV-K env gene in DF-1/K cells during passage. (M) DNAMarker; Lanes 1-5 and 7-10: ALV-K env gene cell-culture passage levels 5, 15, 25, 30, 35, 40, 45, 50, 60, respectively; Lane 6: DF-1 cells (negative control)
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