Practice question

Expression vectors are specifically engineered for efficient transcription and translation of cloned genes in host cells, unlike simple cloning vectors designed only for propagation. They contain strong regulated promoters like T7, lac, or tac, ribosome binding site, translation initiation signals, and often sequences encoding affinity tags such as His6, GST, or MBP upstream or downstream of multiple cloning site to generate in-frame fusion proteins. These tags facilitate solubility enhancement and purification. Cosmids and yeast artificial chromosomes are high-capacity cloning systems for large genomic fragments, not for routine fusion protein production.