Generating tandem repeats by cloning with double initiator fragments

The ability to generate tandem repeats of a DNA sequence has proven importa nt for a large variety of studies of DNA structure and function. The most c ommonly used method to produce tandem repeats involves cloning of an oligom erized monomer sequence that contains asymmetric overlapping ends, but, in practice, this approach is inefficient because of the circularization of ol igomers before they ligate into vector Described here is a method that circ umvents this problem by the use of two separate oligomerization reactions, each containing an initiator fragment onto which monomer polymerizes withou t circularization. Subsequent mixing of the two reactions permits circulari zation, generating a viable plasmid containing the sum of the added repeats from each reaction. A variation of this method is also demonstrated that p ermits the synthesis of constructs with a defined number of repeats.