...packaging genes. However, they are different viruses and require different isoforms of these packaging components...second-generation transfer plasmids as well. Third-generation plasmids include (Figure 4): Transfer plasmid — ...vectors separate transfer, envelope, and packaging components of the virus between different plasmids. The...activate the promoter on the transfer plasmid. Many of the lentiviral transfer plasmids that have been deposited...genes. From an experimental standpoint, the main difference between lentiviruses and gamma-retroviruses is...three (or four, for third generation) plasmids: Transfer plasmid — contains transgene, sgRNA, or shRNA ...systems, due to a wide range of infectivity for different cell types (known as tropism). Lentiviral vectors...