Polycos vectors

A method of producing a phage library of DNA molecules comprising the steps of:

• (a) admixing in a ligation buffer a first DNA segment comprising a sequence of nucleotides that defines a bacteriophage packaging site located between first and second termini capable of being ligated, with a population of preselected second DNA segments in a molar ratio of from about 0.01:1 to about 100:1, respectively, to form a ligation admixture, said second DNA segments being from about 10 to about 20,000 nucleotides in length, said second DNA segments having first and second termini ligatable with said first DNA segment;
• (b) maintaining said ligation admixture under ligation conditions for a time period sufficient to ligate said termini and form a population of concatamerized DNA molecules each having a nucleotide sequence that comprises (i) at least three and no more than 50 copies of said first DNA segment, and (ii) at least two of said second DNA segments;
• (c) forming a bacteriophage packaging reaction admixture by combining the population of concatamerized DNA molecules with a bacteriophage packaging extract in an amount sufficient to package a plurality of the concatamerized DNA molecules;
• and
• (d) maintaining the bacteriophage packaging reaction admixture under packaging conditions for a time period sufficient to package a plurality of the concatamerized DNA molecules and form a plurality of bacteriophage particles each containing at least one DNA molecule, thereby forming said phage library.