BY Preeti Shah | February 09, 2022
DNA fingerprinting has revolutionized the way law enforcement agencies investigate crimes. This technology has proven to be more accurate than any other forensic technique and has helped solve many cases that were once unsolvable.
Individuals might have similar physical features, such as hair color, eye color, shape, or facial features, but their DNA will not be identical. It has increased the likelihood to identify criminals and reduced to a great extent convicting innocent people. Also, modern technology enables storing the DNA profiles in a database that can be quickly searched and compared with that of the suspects.
Here we will have a quick look at what DNA profiling is, the current techniques, and how it proves beneficial to the criminal justice system.
Forensic DNA fingerprinting, also known as DNA profiling, genetic fingerprinting, or DNA typing, is a technique used by lab technicians to determine a connection between a suspect and biological evidence found at the crime scene during a criminal investigation. DNA samples of both the suspect and that found on the crime scene are compared. If both DNA fingerprint profiles match each other, it shows the likelihood of the suspect's involvement in the crime. However, if both samples do not match, the reverse is true.
It was developed by British geneticist Sir Alec John Jeffrey in 1984 at the University of Leicester. The method was used for the first time in the year 1985.
DNA can be obtained from:
5. Skin cells
9. Semen or vaginal cells
There are two types of widely used techniques. These are:
• Restriction Fragment Length Polymorphism (RFLP)
• Polymerase Chain Reaction (PCR)
• A sample of cells, such as blood cells, skin, or hair containing DNA is obtained.
• After that, the DNA is isolated from the cells and is purified.
• The DNA is cut at specific points along the strand with proteins by restriction enzymes to produce fragments. The approach was given by Jeffrey and is based on RFLP (restriction fragment length polymorphism) technology.
• The fragments produced by enzymes are sorted based on their size by placing them on a gel and subjecting it to an electric current (electrophoresis). The shorter fragments quickly move towards the positive anode.
• The double-stranded DNA fragments are split into single strands by subjecting them to a blotting technique. The separated fragments are then transferred to a nylon sheet.
• These fragments are then subjected to autoradiography, where they are exposed to DNA probes. These probes are synthetic radioactive DNA pieces that are bound to minisatellites.
• The fragments are then exposed to a piece of X-ray film. A dark mark is produced at the point at which the radioactive probe is attached.
• The resulting marks pattern is then compared with the known samples and analyzed.
The RFLP technique is highly accurate as the sample size used is more, a fresh DNA sample is used, and there is no amplification contamination.
The RFLP technique is costly, takes longer to complete, and the sample should be large enough to get accurate results.
Polymerase Chain Reaction (PCR) Amplification of Short Tandem Repeats (STRs) Process
The basis of this detection is amplifying several copies of a specific variable region by PCR. PCR is an enzymatic process that repeatedly replicates a particular region of DNA to yield several copies of a particular sequence.
Using gel electrophoresis, these STRs are then amplified and separated with the known repeat sequence. And the distance traveled by them is examined.
A primer which is a short synthetic DNA is designed explicitly for STRs amplification. It attaches to the non-variable region of DNA at the rim of the variable part of the DNA.
PCR amplified STR sequence size is compared with the known samples to deliver the final result.
PCR technique can be carried out with a small amount of specimen, requires less time to complete, and is less costly.
The result is less accurate than RFLP, and amplification contamination is always possible.
Forensic Science: DNA isolated from a biological sample, such as hair, blood, saliva, cells, etc., found at the crime scene are compared with the suspects' samples to establish a connection between the two and help solve the crime.
Paternity/Maternity Identification: Several dispute cases like immigration and inheritance cases can be solved using DNA profiling. It helps in identifying an individual's birth parents.
Personal Identification: No two persons can have the same genetic constitution. Hence DNA fingerprints act like a genetic bar code unique to that person, making the identification process easy.
Hereditary Ailments Diagnosis: It is used to diagnose genetic ailments, such as thalassemia, hemophilia, cystic fibrosis, etc., in newborn babies.
Cure for Genetic Disorders: The DNA fingerprints of a person's relatives having a similar disorder are studied to determine the DNA pattern related to that disease.
Study Evolution Process: It is used to determine the roots of origin of humans and animals by studying the genetic markers passed on to the present generation from their ancestors.
There are many practical uses of this technique. It has played a significant role in forensic science and has helped solve several crimes.
Despite this, there are various shortcomings associated with this technique. If the sample material is not sufficient, it can create errors during the sequencing process. Also, DNA samples can degrade over time, and all these complications can lead to a mixed verdict regarding identity.
It is a powerful tool in forensic science, and hence government must work upon strategies to make constant improvements to enhance the authenticity and transparency of this technique.
DNA fingerprinting in today's legal system is used to determine potential suspects and find their involvement in the crime has enhanced the accuracy process of convicting the criminals. Compared to eyewitnesses, this technique has proved more scientifically accurate and is much less questionable.
Also, despite being highly accurate and playing a significant role in finding criminals, it is only one part of the entire criminal investigation process. There is more than this technique when it comes to convicting a criminal.
So if you want to become a fingerprinting expert, you need to have a clear understanding of the entire criminal investigation process for the overall development of your forensic expert career.
It got established to serve the nation by speeding up the criminal investigation process and train aspiring forensic experts by offering practical training in several forensic science domains.
The hands-on training equips you with knowledge and skills that make you eligible to handle the role of a forensic expert effectively. You can opt for certificate courses and diploma or post-graduate diploma programs as per your educational qualification and requirement. Both online and offline mode of training is available.
They also conduct several workshops and internships from time to time. So do follow their social media accounts to keep yourself updated about the schemes and discounts they offer.