Reviewing an electropherogram, an analyst sees a small extra peak exactly one repeat unit smaller than a strong allele peak, measuring about 10 percent of that allele's peak height. At all other loci the profile shows clean single or paired alleles. How should this peak be interpreted?
- A A stutter artefact of strand slippage during PCR, consistent with a single-source profile ✓
- B Evidence of a second contributor to the sample
- C Allele dropout caused by preferential amplification
- D Pull-up from spectral overlap with another dye channel
Correct answer: A. A stutter artefact of strand slippage during PCR, consistent with a single-source profile
Explanation
Taq polymerase slippage generates stutter products one repeat shorter than the parent allele, typically below 15 percent of its peak height, and they appear reproducibly at multiple loci in single-source samples. Because the peak sits one repeat below a strong allele and stays within expected stutter range, it supports a single contributor. Allele dropout removes peaks rather than adding them, and pull-up appears in the same scan position across dye channels, one repeat below is not its pattern.
Reference: Butler, Forensic DNA Typing, 2nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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