- DNA from a bacterial virus into which is spliced a small fragment of a genome to be amplified and sequenced. A cosmid is an artificially constructed structure. It is used in cloning (copying) pieces of DNA. (On a technical level, a cosmid contains the cos gene of phage lambda and can be packaged in a lambda phage particle for infection into E. coli, permitting cloning of larger DNA fragments that can be introduced into bacterial hosts in plasmid vectors).
* * *A recombinantly engineered plasmid, a circular DNA containing, in order : a plasmid origin of replication and a drug-resistance marker, the cos (cohesive end) site from bacteriophage λ, and a fragment of eukaryotic DNA to be cloned; cosmids are constructed to permit cloning of fragments of up to about 40,000 base pairs in length, with one or more unique restriction sites being necessary to facilitate cloning.
* * *cos·mid 'käz-məd n a plasmid into which a short nucleotide sequence of a bacteriophage has been inserted to create a vector capable of cloning large fragments of DNA
* * *cos·mid (kozґmid) [cohesive end sito + plasmid] a hybrid cloning vector constructed of plasmid DNA joined together with cos sites from a bacteriophage, having advantages of both types of vector and useful for cloning large (up to 50 kb) DNA fragments.
Medical dictionary. 2011.