Two hairs without roots recovered from the same crime scene give identical mtDNA sequences, yet differ from each other at several autosomal STR loci. The most likely explanation is:
- A The hairs come from maternally related individuals, such as siblings ✓
- B Laboratory cross-contamination between the two extracts
- C mtDNA mutates faster than nuclear DNA, creating artificial differences
- D Autosomal STRs cannot be amplified from keratinised tissue
Correct answer: A. The hairs come from maternally related individuals, such as siblings
Explanation
MtDNA is inherited almost unchanged down the maternal line, so siblings and other maternal relatives share an identical or near identical mitotype while their autosomal STR profiles clearly differ. This is precisely the discriminating logic used in kinship assessment. Cross-contamination would tend to blend rather than cleanly separate the marker systems, and nuclear STRs are routinely amplified from hair roots though not reliably from shafts.
Reference: Butler, Forensic DNA Typing, 2nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.