Mechanism of DNA fingerprinting
DNA fingerprinting
DNA fingerprinting is a technique used to identify individuals who have carried out crimes,for determining relationships,for determining inherited diseases and monitoring bone marrow transplants.DNA of every person has the same chemical structure.The difference is in the arrangement of the base pairs in DNA.The sequence of these base pairs is used to identify whether two given DNA are related to each other.
Mechanism of DNA fingerprinting
Step 1:Extraction of DNA from sample cells
The DNA is located inside the nucleus of the cell.Initially, the DNA has to be separated from the rest of the cellular material in the nucleus.This can be done chemically by using a detergent to wash away extra material from the DNA.Inorder to separate DNA from other cellular materials,alcohol is added.DNA moves to the alcohol layer and thus it is separated.
Step 2:Amplification
Amplification is the process of making copies of DNA.This is done by a technique called polymerase chain reaction.
Step 3:Restriction Digestion
DNA is then cut into sections by using resriction enzymes.Resriction enzyme is an enzyme that is found in bacteria which cuts DNA at specific points.
Step 5:Separation of DNA sequences
In this process,the DNA fragments are separated by using gel electrophoresis.The DNA is poured into a gel,and an electric charge is applied to the cell.DNA has a slight negative charge;therefore the pices of DNA will get attracted towards the positive charge(opposite charges are attracted to each other).The smaller pieces will move quickly than the larger ones.thus the DNA will be separated by size.Further by chemical treatment inside the gel,the DNA is rendered as single stranded.
Step 6:Southern blotting
In this process,the separated DNA sequences are then transferred from gel to a nylon membrane.
Step 7:Hybridisation
In this process,the radioactive DNA probes are attached to specific portions of the DNA fragments.Thereafter,any DNA not attached to the probes is washed off.
Step 8:Exposure to X-ray film
The remaining DNA is then exposed to the X-ray film.The radioactive probes on the DNA are allowed to expose the film,which,when developed reveals a unique pattern of dark and light bands.
Sample DNA fingerprint
A sample DNA pttern is shown below.The DNA taken from the crime site and the suspects were undergone DNA fingerprinting.From the pattern obtained,you would be able to identify the criminal.
