Question

How is mitochondrial DNA (mtDNA) typing used in forensic science?
A suspect’s mtDNA sample is matched to an unknown sample of nuclear DNA that was found at a crime scene.
A suspect’s mtDNA sample is matched to an unknown sample of mtDNA that was found at a crime scene.
A suspect’s nuclear DNA sample is matched to an unknown sample of nuclear DNA that was found at a crime scene.
A suspect’s nuclear DNA sample is matched to an unknown sample of mtDNA that was found at a crime scene.

Answer 1

Correct answer:
A suspect’s mtDNA sample is matched to an unknown sample of mtDNA that was found at a crime scene.

Brief explanation:
- mtDNA typing compares the mitochondrial genome sequence from a suspect (or reference person) to mtDNA recovered from evidence (hair shafts, bones, teeth, degraded samples) because mtDNA is present in many copies per cell and survives better than nuclear DNA in degraded material.
- A match indicates the samples are consistent with originating from the same maternal lineage, not necessarily a unique individual, because mtDNA is maternally inherited and identical (or very similar) among maternal relatives.
- Limitations: lower discrimination power than nuclear STR profiling, cannot distinguish among maternal relatives, requires population databases for frequency estimates, and can be affected by heteroplasmy.