Establishing conditions for miniprimer PCR. (A) Minimum primer length. Beginning with a 20-nt primer, a series of shortened primers having a common 5′ end was designed. These primers were used in combination with a 19-nt reverse primer (B) and a 10-nt primer (C) to demonstrate that 10-nt primers can be used for PCR. (B) Amplification using the forward primer series. When electrophoresed on an agarose gel, PCR with S-Tbr produces detectable amplification using primers as short as 10 nt (F10/R19). (C) Miniprimer PCR. Agarose gel electrophoresis of PCR products with S-Tbr and a range of annealing temperatures demonstrates robust amplification for a pair of 10-nt primers (F10/R10). In panels B and C, agarose gels are stained with ethidium bromide and arrows mark the expected size of PCR products.