Somatic mutations at STR loci--a reason for three-allele pattern and mosaicism.

Two families are analysed in which one of the parents exhibited a three-allele pattern at the ACTBP2 locus. Since the alleles were obviously segregated independently to the children, a generalised mosaicism must be assumed involving at least two tissues in one of them and at least four tissues in the other one. The intensity of the PCR amplified alleles in both three-allele individuals indicate an occurrence in a very early embryonic stage. Occurrence was most probably due to a single step mutation in both cases. Forensic implications would include paternity testing as well as stain analysis. Copyright 2002 Elsevier Science Ireland Ltd.