What is the significance of stutter in STR profiles and how is it addressed during interpretation?

What is the significance of stutter in STR profiles and how is it addressed during interpretation?

• A. Stutter is a major peak that represents the true allele.
• B. Stutter peaks indicate contamination.
• C. Stutter is a typical minor peak one repeat shorter; labs model expected stutter percent by locus and account for it during interpretation.
• D. Stutter only occurs in degraded samples.

Answer: (C)

Stutter is a normal PCR artifact in STR profiling caused by small delays or slippage of the DNA polymerase during amplification. The result is a minor peak that runs one repeat shorter than a true allele, often called n-1 stutter, and its intensity is predictable for each locus. Because different loci have different repeat structures and because the peak height of stutter varies, laboratories establish an expected stutter percentage for each locus and instrument. During interpretation, this model is used to decide whether a small peak is a genuine minor allele or simply the stutter from a larger allele. By accounting for this, analysts avoid miscalling additional alleles or misinterpreting heterozygosity, and they can distinguish stutter from potential contamination. Stutter is not a sign of contamination and is not exclusive to degraded samples; it’s a consistent, locus-specific artifact that must be modeled and accounted for in routine STR interpretation.

Stutter is a normal PCR artifact in STR profiling caused by small delays or slippage of the DNA polymerase during amplification. The result is a minor peak that runs one repeat shorter than a true allele, often called n-1 stutter, and its intensity is predictable for each locus.

Because different loci have different repeat structures and because the peak height of stutter varies, laboratories establish an expected stutter percentage for each locus and instrument. During interpretation, this model is used to decide whether a small peak is a genuine minor allele or simply the stutter from a larger allele. By accounting for this, analysts avoid miscalling additional alleles or misinterpreting heterozygosity, and they can distinguish stutter from potential contamination.

Stutter is not a sign of contamination and is not exclusive to degraded samples; it’s a consistent, locus-specific artifact that must be modeled and accounted for in routine STR interpretation.