You guys may hear many news of crime every day. Many cases are also pending in courts. Let's start solving those cases, why you are wasting your time by reading this article. Now you might think, what I am saying right? But, do you know, DNA fingerprinting is directly related to some of those cases? Yes absolutely, Forensic scientists used to do some tests in their labs to find out the culprit and one of those tests is DNA fingerprinting.

DNA fingerprinting is a very famous technique. Initially, Alec Jeffreys developed this method in 1984 in the UK. In India Prof. Lalji Singh first introduced this technique.

Let's discuss the process of this technique. So, for that, we have to know some biological terms like - DNA Polymorphism, VNTR, etc. We all know that DNA is the basis of life. But almost 99.9% DNA of every human is the same. Now, you may say, then what is the difference between me and my friend?? So, the answer is 0.01%. You and your friend have a difference of only 0.01% DNA sequence.

So, from today onwards don't argue with your friend, you both are the same.

Now, we only consider that 0.01% and in this 0.01%, you and your friend have a difference. So, this difference is called DNA polymorphism (Maybe the value of DNA polymorphism is greater for a lion/tiger as compared to us.). In that 0.01%, some DNA sequence is very unique or repeated for someone that is called minisatellite or VNTR (Variable Number Tandem Repeats). The number of VNTR varies in size from 0.1 to 20 kb.

Let's aside these technical terms and try to imagine some movie where you saw some criminal cases. Imagine, a villain killed an innocent guy and fled from that place, then our hero police came and solved the case in his style. In some CID series, you also saw some scenes where police were able to identify the culprit by DNA test. Now, the question is what is the process and how are they able to identify the right culprit by DNA fingerprinting technique?

In the crime spot forensic team try to find some specimen of the culprit like - blood sample, hair, semen, saliva, or body tissue cells. Now, if they can find any of those samples, they come to the lab and start their experiment. But there is another problem that the amount of that sample is very less. So, for that, they use the PCR technique (Polymerase Chain Reaction). By this method, they just amplify the number of DNA and now the sample is ready to use.

Now, they cut the DNA into many pieces and put this into agarose gel. This process is very beautiful. Now, they also take a DNA sample from those persons whom they suspected as culprits. They put all DNA fragments into the agarose gel (There is a separate slot for all samples in the agarose gel plate also). Now, they connect this with cathode and anode plates and start electricity. DNA is negatively charged, so it moves towards the positive plate (Anode). Small DNA fragments move closer to the anode end than large fragments. But human DNA differs by 0.01%. So, all DNA samples will not travel the same distance, because they have little difference.

So, now the question is how do they discriminate between them?? The answer is very easy. If the travel distance of the DNA of any suspect matches with the travel distance of the DNA of the collected specimen from the crime spot, then the culprit will be that suspect. This process is called Gel Electrophoresis. But the process is not over, they collect the DNA fragment in nitrocellulose paper to store the result of the experiment. 

Now, the case is over, police identified the culprit, the movie "The End".

So, you can also do this process very easily now, right?? But don't do this in your home, the kinds of stuff that is used for this technique are very expensive.

If you are a student and want to pursue your career in this field then start studying DNA fingerprinting, this is very interesting.

Thanks for your valuable time, keep supporting.