How DNA FingerPrinting Can Tell Who Killed Who

Click at your own risk…

Fatimah Hussain
4 min readSep 29, 2021

The double helix holds the genetic makeup of every human. An important way to utilize DNA is known is DNA fingerprinting.

Entering a shadowed front, you see a man on the ground. There is red oozing out of the body. You notice a red handprint on the chest of the man, who seems to not have a heartbeat.

What’s a link you can use to potentially catch the killer?

One way would be to go off the red handprint. For simplicity, let’s assume the handprint is of the killer’s.

To achieve this, one can use DNA fingerprinting.



Almost every cell in our body contains our DNA. On average, about 99.9% of the DNA between two humans is the same.

Although this may seem significantly large, it means that there are around three million base pairs that are different between two ordinary people.

Base pairs form one ‘rung’ of the DNA ladder. An example of a base pair is adenine and thymine.

These differences can help you distinguish your genetic makeup from someone else. That’s where DNA fingerprinting comes into action.

DNA fingerprinting is a method used the identify an individual from a sample of DNA by looking at unique patterns in their DNA.

Just like your actual fingerprint, your DNA fingerprint is something you are born with, it’s unique to you, and you only (unless you have an identical twin).

“Is DNA fingerprint = DNA inside your fingerprint?”

Nope!, and you’ll see why…


You might be thinking about those machines that orbit Earth, but the term in this context is something entirely different.


Although there is so much common DNA between humans, there are around 3 million base pairs that are different between two strangers. These are distinguishable with the help of …minisatellites.


Minisatellites are short sequences (10–60 base pairs long) of repetitive DNA that show greater variation from one person to the next.

“How does it connect to DNA fingerprinting?”

DNA fingerprinting is a technique that detects lots of minisatellites in the genome (accumulation of all DNA) to produce a pattern unique to an individual, such as…


The Process

Now that we know the overarching idea, let’s see how we can achieve a DNA fingerprint.

  1. DNA is extracted from a biological sample
  • this can be hair, blood, saliva

2. It uses a polymerase chain reaction (PCR) to produce copies of minisatellite sequences

  • PCR is able to create countless copies of a specific DNA sequence. They do this to make the samples longer for easier study.

3. When adequate copies of the sequences have been produced, those DNA strips are mixed into a gel.

4. Then they run an electric current through the gel, which separates smaller strands of DNA from the larger ones.

5. A dye added to the gel makes the DNA strips stand out when they’re placed against an ultraviolet light or lit up with a laser.

6. The strips will show a (usually) barcode-like pattern that can then be compared to the results from another sample of DNA to find a match.



DNA fingerprinting can be used to establish a link between biological evidence and a criminal suspect. It’s done like the following:

  1. The DNA sample taken from a crime scene is compared with a DNA sample from a suspect.

If the DNA profiles match:

  • The evidence came from that suspect.

If not:

  • The evidence is not from the suspect.


Amid the breakthrough of DNA fingerprinting, there’s been speculation on its reliability at putting a person to a DNA fingerprint, and doing it accurately.
But this topic deserves its own page, as it's still being questioned to this day.

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Fatimah Hussain

An AI+ML+CAD Software Design Enthusiast. Striving to Create an Everlasting Impact.