Mutation rate evaluation at 21 autosomal STR loci: Paternity testing experience.

Area of Science:

• Forensic Genetics
• Human Genetics
• Molecular Biology

Background:

• Short tandem repeats (STRs), also known as microsatellites, are highly polymorphic DNA sequences.
• STRs are widely utilized in forensic science, particularly for paternity testing, due to their high mutation rate compared to bulk DNA sequences.

Purpose of the Study:

• To investigate and quantify the mutation rates across 21 autosomal STR loci in a cohort of 746 paternity cases.
• To determine locus-specific mutation rates and understand the spectrum of mutational events (single-step vs. multi-step).

Main Methods:

• Analysis of 746 paternity cases involving 21 autosomal STR loci.
• Identification and characterization of observed mutations within these STR loci.
• Estimation of overall and locus-specific mutation rates.

Main Results:

• A total of 41 mutations were detected across 11 STR loci, with the highest mutation rate observed at the SE33 locus.
• No mutations were recorded in the remaining 10 STR loci.
• The overall average mutation rate was calculated as 0.004523, with locus-specific rates ranging from 0.001214 to 0.016990.
• Single-step mutations accounted for 90.24% of all observed mutations, followed by three or multi-step (7.32%) and two-step (2.44%) mutations.

Conclusions:

• The study provides critical data on autosomal STR mutation rates, essential for refining DNA testing interpretation.
• Understanding mutation dynamics, especially at loci like SE33, enhances the accuracy and reliability of paternity testing and other forensic applications.
• The characterized mutation rates contribute to the ongoing development and validation of genetic analysis methodologies.