Learn how DNA fingerprints help identify individuals, solve crimes, and trace ancestry. A key topic in daily GK updates and competitive exam news.

What is DNA and Why is It Unique?

DNA (Deoxyribonucleic Acid) is the hereditary material present in almost every cell of the human body — from bones to blood, skin to saliva. Each person (except identical twins) has a unique DNA structure, making it an excellent tool for identification, especially in crime scenes, disaster sites, and ancestry tracing.

Each human cell carries 46 DNA molecules — 23 from the father and 23 from the mother — packed in chromosomes. Differences in DNA, called polymorphisms, are what make each individual genetically unique.

What Are DNA Polymorphisms?

Polymorphisms are small variations in the DNA sequence that differ from person to person. These differences are found in specific parts of the chromosome and are crucial in DNA profiling.

For example:

Chromosome 3 carries about 6.5% of total DNA.

The maternal and paternal chromosome 3 versions are similar but have slight variations (polymorphisms).

These help trace ancestry, determine relationships, and differentiate individuals.

What Are STRs and Why Are They Important?

STRs (Short Tandem Repeats) are sequences in DNA that repeat multiple times. The number of repeats varies across individuals, making STRs highly polymorphic.

For example:
One person might have the repeat GATC 4 times, while another might have it 7 times.

🔹 STRs are the most commonly used polymorphisms in forensic DNA analysis and are a foundation for DNA fingerprinting.

How Is DNA Copied Using PCR?

To analyze DNA, scientists need millions of copies of a small DNA segment. This is done using the Polymerase Chain Reaction (PCR):

Heat the DNA to separate its strands.

Add primers – short DNA sequences that target specific STRs.

Add Taq Polymerase, which builds the complementary DNA strand.

Repeat for multiple cycles in a thermocycler to amplify the DNA.

Even from a tiny sample (blood, sweat, or spit), millions of copies can be made in under an hour.

What is Capillary Electrophoresis?

Once STRs are amplified, they're separated by size using capillary electrophoresis:

DNA fragments move through a capillary under an electric field.

Smaller fragments move faster than larger ones.

The results are compiled into a DNA fingerprint — a unique genetic identity card.

Applications of DNA Fingerprinting in Real Life

DNA fingerprinting has revolutionized forensic science and genealogy:

Forensic and Legal Use

Identify disaster victims using teeth, bones, or blood.

Solve cold crime cases using archived samples.

Identify suspects from bloodstains or saliva at crime scenes.

Prove parent-child relationships.

Exonerate innocent convicts (source: The Hindu).

Medical and Research Applications

Match organ donors and recipients.

Trace ancestry and genealogy.

Understand mutation rates in genetics.

Key Takeaways

DNA polymorphisms help differentiate individuals genetically.

STRs are repeated DNA sequences used in DNA profiling.

PCR is used to amplify DNA even from tiny samples.

Capillary electrophoresis separates DNA fragments for fingerprinting.

DNA can remain intact for over 65,000 years and still be used for identification.

DNA fingerprints are as unique as Aadhaar numbers for biological identification.

Related Resources for Students

For additional references, you may read the PIB update on Forensic Technology and The Indian Express article on DNA forensics.

Why This Matters for Exams

Topics like DNA fingerprinting, PCR, and STRs are frequently asked in UPSC Prelims, MPPSC, SSC, and Banking GK sections under Science & Tech and Current Affairs. Understanding these terms not only helps in exams but also gives real-world insight into how science and law intersect.

Stay updated with more such daily GK updates and current affairs March 2025 articles on Atharva Examwise current news to stay ahead in your exam preparation.

Keep learning. Keep growing. Team Atharva Examwise