Generation of Clones - Recombinants are usually constructed using a large and complex mixture of potential inserts or genes of interest, thereby generating an extensive collection of clones. The desired recombinant is finally obtained by specific selection and screening procedure.

Both procedures become much easier if the initial mixture is partly enriched for the segment of interest because fewer recombination clones have to be tested to find the desired end.

There are four sources of inserts for cloning.