In forensic science, how is mitochondrial DNA (mtDNA) typing most commonly used?

• A. To determine a suspect’s Y-chromosome haplotype to trace paternal lineage using markers found only in males
• B. To analyze the hypervariable regions of mtDNA, which is abundant and maternally inherited, enabling identification from degraded samples such as hair shafts, bones, and teeth
• C. To uniquely identify individuals by profiling highly polymorphic STR loci in nuclear DNA, which is inherited from both parents
• D. To measure the number of mtDNA molecules per cell to estimate a person’s age at the time a biological sample was deposited

Answer: (B)

Verified step by step guidance

1. Understand the unique properties of mitochondrial DNA (mtDNA): it is maternally inherited, present in many copies per cell, and contains hypervariable regions that differ between individuals.
2. Recognize that mtDNA is especially useful in forensic cases where nuclear DNA is degraded or insufficient, such as in hair shafts, bones, and teeth.
3. Know that mtDNA typing focuses on analyzing the hypervariable regions to establish maternal lineage or identity, rather than paternal lineage or individual-specific nuclear DNA markers.
4. Differentiate mtDNA typing from Y-chromosome analysis, which traces paternal lineage and is only applicable to males, and from nuclear DNA STR profiling, which is used for unique individual identification.
5. Conclude that mtDNA typing is most commonly used to analyze the hypervariable regions of mtDNA for identification purposes in degraded samples, leveraging its abundance and maternal inheritance.