|Primers are short single-stranded DNA sequences used as a starting point for PCR amplification or sequencing. Primers effectively "direct" DNA polymerases where to begin replication of DNA, because DNA replication can only add additional nucleotides to an existing strand of DNA, not start from scratch. Primers are typically around 20-30 nucleotides in length and are composed of at least 40% G's and C's. There are a variety of online tools available to help you design new primers to your DNA template of interest. Since primers are so short, they can be readily constructed via chemical synthesis. Commercial primer synthesis is cheap and fast, so no primers are distributed with the Registry collection.