Fig 1

Location of PCR primers flanking the CAG repeat region of the HD gene. The CAG trinucleotide repeats are indicated by shaded boxes. Calculation of the number of CAG repeats is specific to the primers used. The forward and reverse primers used by each laboratory are indicated. The numbers next to each primer correspond to individual laboratories. Primer set 11 (NIST) was used for amplification and DNA sequence analysis. The arrows indicate the direction of DNA synthesis from the primers. Primers used to measure the CCG repeats are not shown but are described in “Methods.”