Syllabus:
GS3: Science and Technology- Developments and their Applications and Effects in Everyday Life.
Context:
Recently, DNA tests has been carried out in large number to identify the dead bodies of victims of the Air India flight crash.
More on the News
- At least 270 people, mostly passengers, died on June 12 when Air India flight 171 crashed shortly after takeoff from Ahmedabad.
- DNA tests are being used to identify the victims, with most remains already matched using family samples collected over the past week.
DNA Analysis
- DNA analysis, also known as DNA profiling or DNA fingerprinting, is a scientific technique used to identify individuals based on their unique genetic makeup.
- DNA fingerprinting identifies individuals by examining unique segments of their DNA.
- Although 99.9% of human DNA is identical, the remaining 0.1% contains variations known as short tandem repeats (STRs).
- These highly variable sequences serve as key genetic markers in forensic investigations, except in identical twins who share the same DNA profile.
Short Tandem Repeats (STRs):
- An STR is a short sequence of base-pairs on the DNA that is repeated some number of times.
- STRs are often polymorphic. Unrelated individuals almost certainly have different numbers of repeat units in at least some STRs.
How to make copies of DNA
- Polymerase Chain Reaction (PCR) is a method scientists use to make many copies of a specific part of DNA, even from a tiny sample.
- First, they heat the DNA to separate its strands. Then, they add short DNA pieces called primers, which stick to the part they want to copy.
- A special enzyme called DNA polymerase helps build new strands by adding matching bases.
- This process happens in a machine called a thermocycler, which changes the temperature automatically.
- By repeating these steps many times, scientists can create millions of copies quickly. PCR is often used to study certain DNA regions like STRs.
Applications of DNA Analysis
- DNA Fingerprint can establish parent/child relationships and help identify individuals from their mortal remains at disaster sites.
- DNA from blood stains, sweat, and spit from cloth or soil, retrieved from crime scenes, can be used to identify suspects.
- Experts also use them to identify or exclude potential donors during organ donation.
- It helps to reconstruct ancient populations and lineages.
- It helps to identify genetic predispositions to diseases and understand diversity.
Challenges Associated with DNA Analysis
- Environmental Factors: DNA easily degrades under environmental stress like heat, humidity, sunlight, and microbes. In mass disasters or prolonged exposure, samples may become fragmented or too damaged for analysis.
- Time Since Event: The longer a sample has been exposed or a person has been dead, the higher the chance of DNA degradation, making it a key challenge in cold cases and historical investigations.
- Sample Type and Storage: Soft tissues break down faster than hard tissues like bones and teeth, which better preserve DNA. Poor collection, handling, or storage can speed up degradation and cause contamination.
- Low Template DNA (LTDNA): Crime scenes or degraded remains often yield only tiny amounts of DNA. Analyzing such low-template DNA is challenging due to higher contamination risk and difficulty in interpretation.
Way Forward
- Developing advanced techniques for analyzing degraded and low-template DNA, as well as rapid and cost-effective methods, is crucial.
- Enforce strict national guidelines for DNA collection, preservation, and analysis to ensure accuracy across all forensic labs.
- Introduce robust laws that balance DNA use with privacy rights, ensuring secure databases and preventing misuse.
- Invest in training law enforcement, forensic experts, and legal professionals to improve their use and understanding of DNA evidence.
Mains Question
Discuss the importance and applications of DNA analysis in modern science, with a special focus on forensic investigations. What are the challenges associated with it? Suggest suitable measures to address them. (15M, 150W)