DNA matching (also called DNA profiling or DNA fingerprinting) is done to compare DNA sequences between individuals to check if they are genetically related or to identify someone uniquely (like in crime scenes or paternity cases). Here's how the test is done, step-by-step, in simple terms:
🔬 Steps of DNA Matching Test
1. Sample Collection
DNA can be taken from:
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Blood
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Saliva (cheek swab)
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Hair roots
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Skin cells
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Semen, sweat, or other body fluids
Usually, for routine matching (like paternity), a cheek swab is used—painless and quick.
2. DNA Extraction
The collected cells are broken open in a lab to release DNA.
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Chemicals or enzymes are used to isolate DNA from other cell parts.
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DNA is then purified and collected.
3. DNA Amplification (PCR)
The sample DNA is often very small.
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Using a method called PCR (Polymerase Chain Reaction), specific regions of the DNA are copied many times.
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This creates enough material to work with.
4. Analyzing Specific DNA Regions
DNA is 99.9% same in all humans. But in certain regions, called Short Tandem Repeats (STRs), the number of repeats varies from person to person.
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Scientists examine 13 to 20 STR markers (e.g., “ATCG” repeated 5 times in one person, 7 times in another).
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These STRs are like barcodes that differ between individuals.
5. Gel Electrophoresis or Capillary Electrophoresis
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STR fragments are loaded into a gel or capillary system.
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An electric current is passed.
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Based on size, the DNA fragments move differently.
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This produces a DNA profile – a pattern of bands or peaks.
6. Matching the Profiles
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The DNA profile from one sample is compared to another.
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If all STR regions match perfectly, it’s a match.
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In paternity testing, the child’s STRs should all match either the mother or the alleged father.
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In forensics, DNA from the crime scene is compared to a suspect’s.
🔍 Accuracy
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For identity or paternity, the chance of error is extremely low (greater than 99.99% accuracy if enough markers are tested).
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In legal and forensic uses, matching 13–20 STR markers gives near-certain identification.
📦 Summary Box
| Step | What Happens |
|---|---|
| 1. Sample | Collect DNA from body cells |
| 2. Extract | Isolate DNA from sample |
| 3. Amplify | Make more DNA using PCR |
| 4. Analyze STRs | Look at repeating DNA parts |
| 5. Electrophoresis | Visualize and create DNA profile |
| 6. Compare | Match profiles for identity or relation |