Short tandem repeat mutations in paternity analysis

Abstract

Polymorphic autosomal short tandem repeats (STRs) are a class of genetic markers that are routinely being used for parentage testing purposes in forensic science laboratories. They are composed of tandemly arranged repeat units (typically 2-7 bp in length) and are widespread throughout the human genome. Among the various types of repeats, tetranucleotide repeats have become the widely utilized systems due to their specific advantages. STRs have become markers of choice in Forensic DNA typing due to the ease with which they can be studied. STR DNA typing involves amplification using Polymerase Chain Reaction (PCR), capillary electrophoresis, and subsequent detection of the amplified fragments using laser-induced fluorescence of the size-separated DNA fragments. A panel of STR markers are being routinely used to solve paternity and kinship cases. Together with lineage markers such as Y-STRs and mitochondrial DNA (mtDNA), they form a formidable set of markers that can resolve disputed paternity cases with high confidence. Nevertheless, ambiguous results can be obtained in a proportion of cases due to incompatible genotypes between the disputed parent and the child, which requires careful interpretation of the DNA typing results. We finish this chapter by discussing a difficult paternity dispute case in which the concurrent paternal and maternal inconsistencies were observed in the questioned child.