Amplification of cosmid libraries may result in distorted representation of cloned genomic sequences and should be avoided wherever possible. In this method of amplification, distortion of the library is rarely a problem because at no stage are bacteria containing different recombinant cosmids grown in competition with one another. - [Read Amplification and Storage of a Cosmid Library: Amplification on Filters Protocol]
Protocol describes how to construct a library of 35-45-kb fragments of genomic DNA in the double cos site cosmid vector, SuperCos-1. The steps include: Linearization and dephosphorylation of SuperCos-1 DNA; Partial digestion of high-molecular-weight DNA with MboI; Dephosphorylation of high-molecular-weight genomic DNA; Ligation of cosmid arms to genomic DNA: Packaging and plating recombinants; Isolation and analysis of recombinant cosmids: Validation of the library. - [Read Construction of Genomic DNA Libraries in Cosmid Vectors Protocol]