Cosmid vector
They were developed in the late 1970s and have been improved since. They carry one, or more cos sites .Cosmids combine essential elements of a plasmid and Lambda systems. Depending on the aim of the experiment there is broad host range cosmids, shuttle cosmids or 'mammalian' cosmids (linked to SV40 oriV and mammalian selection markers) that are available. Fragments from 30 to 46 kb can be accommodated by a cosmid vector. A cosmid is basically a plasmid caring cos site. Recombinant cosmid is injected into the bacterial cell where the rcosmid arranges into a circle and replicates as a plasmid. It can be maintained and recovered just as plasmids.
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