DNA Identification Techniques

Source:  IE

Context: After the tragic Air India Boeing 787 crash in Ahmedabad, authorities are using DNA identification techniques to confirm the identities of the deceased.

About DNA Identification Technique:

• What is DNA Identification?
  • DNA identification is the forensic process of matching DNA from unidentified human remains with known biological samples.
  • Each individual’s DNA (except identical twins) is unique, making it a biological fingerprint used to establish identity with high precision.
• How DNA Identification Works?
  • Sample Collection & Storage:
    • DNA begins to degrade after death, especially in hot/humid conditions.
    • Investigators collect DNA from hard tissues (bones, teeth) or soft tissues (skin, muscle), storing them in ethanol or freezing at -20°C to prevent breakdown.
  • Reference Matching:
    • Reference DNA is collected from close relatives (parents, children, maternal or paternal kin) or personal items (toothbrush, hairbrush) for comparison.
    • Matching determines the relationship and helps confirm the identity of the remains.
  • Methods of DNA Analysis:
    1. Short Tandem Repeat (STR) Analysis:
       • Evaluates repeating sequences in nuclear DNA.
       • Most commonly used; accurate if DNA is well preserved.
    2. Mitochondrial DNA (mtDNA) Analysis:
       • Used when nuclear DNA is degraded.
       • Inherited maternally, so it’s matched with maternal relatives.
    3. Y-Chromosome STR Analysis:
       • Traces paternal lineage using male-specific Y chromosomes.
       • Useful when close maternal relatives are unavailable.
    4. Single Nucleotide Polymorphism (SNPs):
       • Detects single-point mutations in highly degraded DNA.
       • Less accurate than STR but useful when reference DNA is minimal.

• Key Features and Applications:
  • Gold Standard: Preferred in mass disasters, wars, plane crashes, and crime scenes.
  • Accuracy: High specificity; can differentiate individuals even from degraded remains.
  • Storage Sensitive: Requires strict protocols for preservation to avoid data loss.
  • Universal Use: Employed by agencies worldwide, including CBI, INTERPOL, and ICRC.
  • Legal Validity: DNA evidence is admissible in Indian courts under the Indian Evidence Act.