... multiple plasmids. Second generation packaging systems use 3 plasmids; an envelope plasmid that usually...encodes VSV-G, a packaging plasmid containing structural genes and a transfer plasmid carrying the transfer...Rev gene from the packaging plasmid and incorporating it into a fourth plasmid. In addition, the promoter...and packaging plasmids in order to obtain the best titers. Requiring an additional plasmid for transfection...high titer virus for transfer plasmids with small inserts (such as CRISPR guides) while a single 72h harvest...By dividing the viral elements across multiple plasmids, the risk of recombination and consequently, the...extra level of safety, they also require a fourth plasmid. The requirement for additional DNA can impact ...