SMRT sequencing of a full mutation allele of (nominally) 750 CGG repeats. (A) Representative CCS sequences from a library of PCR-amplified FMR1 genomic DNA. These reads are the result of reading through >2 kb of CGG repeats at least three times. (B) Size-corrected distribution of sequence lengths in the sequenced library plotted by region. PCR amplification creates a broad distribution of repeat sizes with a mode at 720 repeats.