A forensic case involves a hair shaft without the root. Which type of DNA analysis is MOST appropriate, and what is its key limitation compared to nuclear STR profiling?

• A Autosomal STR; limitation is insufficient copy number in shed hairs
• B Mitochondrial DNA sequencing; limitation is it cannot distinguish maternal relatives ✓
• C Y-STR profiling; limitation is it only applies to male donors
• D SNP array; limitation is cost and time

Explanation

Shed hair shafts lack nucleated cells and therefore have insufficient nuclear DNA for autosomal STR profiling; mitochondrial DNA analysis is used instead. The key limitation of mtDNA is that it is maternally inherited, so it cannot distinguish between individuals sharing the same maternal lineage (e.g., a mother and her children, or maternal siblings all share identical mtDNA sequences in the absence of heteroplasmy). Nuclear STR (A) fails because of the copy number issue, not just methodology. Y-STR (C) would only address paternal line males. SNP arrays (D) are not the standard tool for shed hair.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

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Written and medically reviewed by the StethoPrep medical team.