#322: How DNA analysis help identifying victims?

DNA analysis techniques simplified!

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1. Collection and Storage of Samples

• Source: DNA is collected from individual dies, especially after plane crashes, where tissue samples from wreckage are used.

• Degradation: DNA begins to degrade over time, making analysis difficult or impossible, especially in dry conditions or when hot and humid.

• Storage Conditions: Samples (e.g., soft tissues like skin, muscles, etc.) may be stored at 20-degree Celsius or in the case of soft tissues (95% ethanol).

• Preferred Tissue: Investigators usually collect DNA from soft tissue for better preservation.

2. Methods of Analysis

• Short Tandem Repeat (STR) Analysis:

  • Evaluates short tandem repeats, which are essentially short repeating sequences of DNA.

  • STRs are used for DNA identification as they vary widely between individuals.

  • Effective after analyzing 15 or more of these hyper-variable regions.

  • Used by the International Committee of the Red Cross (ICRC) for identification.

• Mitochondrial DNA (mtDNA) Analysis:

  • Found in the cell's energy-producing organelles (mitochondria).

  • Passed on from mother to son, making it useful for maternal lineage identification.

  • Useful when nuclear DNA is degraded or insufficient.

• Single Nucleotide Polymorphisms (SNPs) Analysis:

  • Involves analyzing variations at a single base (A, C, G, or T) in the DNA sequence.

  • Unique to each person, aiding in identification.

  • Often used with samples from mother-child pairs or paternal relatives.

  • Less effective than STR due to lower variability.

3. Applications

• Identification: STR and mtDNA used to identify victims of tragedies (e.g., September 11, 2001 attacks in New York).

• Forensic Science: Helps establish relationships (e.g., high degree of confidence in parent-child relationships).

• Maternal and Paternal Lineage: mtDNA traces maternal lines; SNPs help match with relatives.

4. Challenges

• Degradation: DNA from soft tissues degrades much faster than hard tissues (bones and teeth).

• Sample Quality: Success depends on the quality of DNA extracted, with scientists aiming for 50% or more shared DNA among samples.

5. Key Organizations

• International Committee of the Red Cross (ICRC): Utilizes STR analysis for identification in conflict zones.

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