THE CODE OF IDENTITY: Unlocking the secrets of DNA matching

What is DNA matching?

DNA matching (also called DNA profiling or DNA fingerprinting) is the process of comparing DNA samples to determine if they come from the same individual or are biologically related. It utilizes the unique genetic code in an individual’s DNA to establish identity.

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Procedure of DNA matching

1. Sample collection: Biological materials such as blood, saliva, semen, skin cells, hair follicles, bones, etc., are collected from:

• Crime scenes
• Dead bodies
• Suspects or relatives

2. DNA extraction: DNA is isolated from the collected sample using chemical processes.
3. Quantification: The amount of DNA is measured to ensure enough material is available for testing.
4. Amplification via PCR (Polymerase Chain Reaction): Specific regions of DNA (Short Tandem Repeats or STRs) are amplified to create a DNA profile.
5. Separation and detection: The amplified DNA fragments are separated using gel electrophoresis or capillary electrophoresis.
6. Profile generation: A digital DNA profile is created based on the STR markers.
7. Matching: The generated profile is compared with:

• A known suspect’s DNA
• A DNA database (like India’s proposed NDNADB)
• Family members' DNA (in body identification)

Functions & importance in forensics

1. Criminal investigations: Matches DNA from crime scenes with suspects; exonerates the innocent.
2. Identification of unidentified bodies: Matches DNA from decomposed/charred bodies with family members.
3. Paternity and kinship tests: Used in custody battles and missing person cases.
4. Mass disaster victim identification: Useful in earthquakes, plane crashes, etc.
5. Wildlife forensics: Identifies poached animals and illegal trade.

Time taken for DNA matching

Context                                   Time taken

Routine Lab Test                    1–2 weeks

Urgent Forensic Cases            24–72 hours (fast-tracked)

Mass Disaster ID                    Weeks to months (depends on scale and condition of samples)

Limitations of DNA matching

1. Sample contamination: Poor handling can lead to inaccurate results.
2. Degraded DNA: Fire, decomposition, or chemicals may damage DNA.
3. Partial matches: Especially in mixed or low-quality samples.
4. Cost and time: High-end machines and trained experts are needed.
5. Privacy issues: Storing DNA in databases raises ethical concerns.
6. Legal and ethical challenges: Admissibility in court requires strict chain of custody.

Body identification vs criminal identification: Key differences

Factor                         Body identification                            Criminal investigation

Sample source             Bone, tooth, tissue from deceased      Blood, hair, skin cells from crime

scene

Comparison sample     From relatives (for kinship match)      From suspect or DNA database

Time required              Longer (if DNA is degraded)             Usually quicker (especially with

fresh sample)

Goal                            Establish identity                                Establish guilt or innocence

Complexity                 High in case of mass graves                Complex in cases of multiple

suspects

Civil Services Examination Questions

Prelims (Objective)

1. Which of the following techniques is used in DNA profiling?
2. A) Gel Electrophoresis
3. B) PCR
4. C) Spectrophotometry
5. D) Both A and B

Answer: D

2. DNA matching is NOT useful in which of the following cases?
3. A) Paternity testing
4. B) Age determination
5. C) Identifying disaster victims
6. D) Criminal investigations

Answer: B

Mains (short/long answer)

1. Short answer (150 words):

Describe the process and significance of DNA profiling in forensic science.

2. Long answer (250–300 words):

Discuss the role of DNA matching in criminal investigations and mass disaster victim identification. What are the challenges and limitations associated with it?

3. Long analytical (300+ words):

Critically analyse the implications of DNA technology in the criminal justice system. How can India balance its utility with privacy and ethical concerns?

Interview (Personality Test)

1. How reliable do you think DNA evidence is in the Indian legal system?
2. Should the government maintain a national DNA database? What are the pros and cons?
3. Can DNA evidence alone be sufficient to convict a person? Why or why not?