Ultramer primers are oligonucleotides that range in length from 25–200 bases. These long primers are especially useful in PCR and site-directed mutagenesis reactions. Incorporating Ultramer Oligonucleotides as the mutagenic primers allows for greater flexibility in the type and size of sequence changes that can be made. The 3’ end of the Ultramer oligonucleotide primes the PCR with the additional sequence placed upstream (5’).
Researchers can now add long stretches of new sequences to an existing clone by adding up to 180 bases to a 20-base PCR primer. This enables addition of elements such as protein purification tags (e.g., 6X His) or bacterial phage promoters (e.g., T7/T3/SP6) for in vitro RNA transcription. In addition, Ultramer primers provide the means to make changes to a large area within a clone in a single reaction or change or correct multiple sequence locations simultaneously. Finally, Ultramer primers provide a new tool for regions that have traditionally been difficult to target by extending primers into regions with more optimal sequence composition than was previously attainable.