About 25% of cALL patients have the TEL-AML1 gene fusion derived from the t(12;21) chromosomal translocation.     ///    These results confirm previously published findings of a prenatal origin of TEL-AML1 in Europe by demonstrating its occurrence in a California-born population.     ///    The aim of our study was to determine whether TEL-AML1 fusions arise prenatally in a U.S.     ///    "Clonotypic primers were designed for each patient breakpoint, and a nested PCR assay was used to determine the presence of the TEL-AML1 fusion sequence in neonatal Guthrie cards. "