(B) PCR and Southern blot analysis of Er81EWS-Pea3 wild-type (+/+), heterozygous (+/−), and homozygous (−/−) genomic DNA to detect the mutant allele. PCR primer pairs (EWS-Pea3ki) were used to detect specifically the recombined allele, and a primer pair in exon2 was used to detect the presence of the wild-type allele [14].