Which vector includes Cos sites from lambda phage?
Cosmid vectors combine plasmid origin and lambda phage cos site required for packaging into phage heads. Cos sites are 12 base sticky cohesive ends that direct concatemer cleavage during lambda packaging. Incorporating cos sequence enables in vitro packaging of recombinant DNA flanked by cos sites into infectious lambda particles, allowing transduction into Escherichia coli with high efficiency. This permits cloning of 37-52 kb inserts larger than standard plasmids but smaller than BACs. Cosmid retains plasmid replication and antibiotic selection, merging phage delivery with plasmid maintenanc
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
