Fig. 5.

Detection and validation of variants present in a minor fraction of the DNA population. (A) Mixtures of PCR products containing 0–4% L alleles of MID42 were used for BEAMing. Flow cytometry such as that shown in Fig. 3 was used to determine the fraction of singlet beads that were red (y axis). The proportion of singlet beads that hybridized to at least one of the probes varied from 3.2% to 4.3%. (B and C) Beads were sorted with the FACSVantage SE instrument, and individual red or green beads were used as templates for conventional PCR by using the forward and reverse primers listed in Table 1. Red beads generated only the S allele sequence, whereas green beads generated only the L allele sequence.