DNA Fingerprinting: The Technique Used For Paternity Tests & To Identify Criminals
A technique where in a unique pattern about an individual can be identified using various techniques is called DNA fingerprinting. It is a method where you can identify, characterize and classify organisms. Most of the DNA is similar in humans but only 0.1% is different which us all so different from each other.
But is why only DNA is considered? Why not anything else? DNA remains constant and same throughout and is very stable. Most of the genome is repetitive and only a few percentage is made of genes.
The DNA fingerprinting can be used to solve crimes and in paternity dispute cases.
The DNA is extracted from the body and then is amplified using Polymerase chain reaction.
gel electrophoresis or sequencing can help n fragmenting the DNA.
The sequence of those particular regions which are different amongst humans based on the DNA print can be prepared.
The various molecular tools are able to create exact patterns of an organisms DNA.
Real time PCR and DNA sequencing are very powerful and fast.
How DNA fingerprint is created?
Each individual is genetically unique (except identical twins). Most DNA varies very little between individuals but some of the existing variation may result in genetic disease. However, ‘‘silent’’ parts of chromosomes contain regions of extreme variability that have no effect on the individual; these regions which are scattered along chromosomes are referred to as ‘‘minisatellites’’. Procedures for the detection of these minisatellites allow identification of each individual by DNA fingerprinting. Depending on the DNA probe used, individual-, population-, or species-specific DNA fingerprints may be generated.
DNA fingerprints may be revealed using a variety of methods. Some of the methods used for the generation of DNA fingerprints rely on DNA: DNA hybridization either with a microsatellite probe or with a single-locus probe. Such methods involve isolation of the DNA from a sample and cleavage of the DNA with restriction enzymes to generate millions of different fragments which are separated by gel electrophoresis; following treatment to separate the two strands of the double helix in each DNA fragment, Southern blotting is used to transfer the single- stranded DNA from the gel to a membrane without disrupt- ing the pattern in the gel. The membrane is incubated with a radioactive DNA probe — a segment of single-stranded DNA that detects and forms a double helix with any DNA fragments on the membrane containing minisatellites.
Steps involved in DNA fingerprinting
DNA test Tube
Sample collection from blood, saliva, hair
Extraction of DNA
Agarose gel electrophoresis, DNA sequencing
1st step : collection of the sample
DNA is extracted from body fluids, hair etc. In cases of crime a buccal swab can be taken.
A blood sample is better than a buccal swab and yields better results.
2nd step: DNA extraction
First DNA is obtained. If DNA is of good quality and quantity then good results are obtained.
DNA can be extracted by Phenol-chloroform DNA extraction method
Use DNA extraction kit for DNA fingerprinting.
3rd step : Digestion, amplification or DNA sequencing
most commonly used are:
PCR based analysis
Real-time PCR analysis
PCR based analysis:
PCR based DNA fingerprinting is the most widely used. It is cheap, most reliable, and fast.
Real-time PCR analysis:
It counts the number of amplicons, which are repeated.
This technique often solves many crimes and is cheap, reliable, and fast.
4th step: analysis of the results obtained
By using the southern blotting, and DNA sequencing, DNA profiling results can be obtained in which rt-PCR and sequencing are often used in forensics.
5th step: Interpretation of the results
Interpretation of the results is totally automated and the computer interprets the result.
DNA fingerprinting uses
DNA fingerprinting uses
If a persons identity has to be validated then DNA fingerprinting is ideal.
When the body is damaged badly like in cases of death or crime, DNA fingerprinting comes in handy.
One of the most popular and essential use of DNA fingerprinting is in the field of crime. DNA is collected from the crime scene either from saliva, blood or hair. The criminal’s connection to the crime can be known when DNA patterns are matched.
Blood relatives can be identified
To know the association between two individuals, whether they are related or not can be done by this technique.
It can also be used to know about any inherited disease or any genetic abnormality or disorder.