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What is DNA Fingerprinting?

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Also referred to as DNA profiling. The laboratory process known as DNA fingerprinting uses the nucleotide sequences of particular regions of human DNA that are unique to each person to determine a person’s likely identification. DNA fingerprinting is used in criminal investigations, paternity testing, and other forensic applications. The objective in these situations is to “match” two DNA fingerprints, such as a DNA sample from a known individual and one from an unknown individual. It is a forensic method that has been applied to the zoological, botanical, and agricultural studies of animal and plant populations. For example,

If you want to identify a criminal at a crime scene, DNA fingerprinting will work as a means to rectify the identification of the criminal.

  1. We collect DNA samples from the crime scene.
  2. Then we collect the DNA samples of the suspects.

Through the process of DNA fingerprinting, we will try to identify who is a criminal among our suspects.

DNA Fingerprinting


From the above, we can conclude that the criminal is Suspect 2.


Sir William Herschel was the first to employ DNA fingerprinting as a method of identification in 1858. To identify the DNA sequences discovered between genes and identify the markers for inherited diseases so that they can be treated early, Dr. Alec Jeffreys developed the DNA fingerprinting technology at the University of Leicester in the United Kingdom in 1984. He was unaware at the time that the same method would eventually be used to help solve murder cases or paternity trials. Later, DNA fingerprinting technology was developed in India at the CCMB (Centre for Cell and Molecular Biology), Hyderabad, by Drs. V.K. Kashyap and Lalji Singh.  Dr. Lalji Singh is the Father of Indian Fingerprinting, while Dr. Alec Jeffreys is the Father of DNA Fingerprinting.


The combination of DNA sequences that frequently differ significantly between people is identified by DNA fingerprinting or DNA profiling.

  • Short nucleotide repeats that are inherited and vary in number from person to person are the most crucial need for DNA fingerprinting. These are referred to as VNTRs or variable number tandem repeats.
  • The DNA fingerprinting method is based on the idea that nobody has an identical DNA sequence, except for identical twins (monozygotic twins).


Step 1- DNA Isolation

DNA is taken from the cell and purified via chemical processing and centrifugation.

Step 2- Amplification

Using the polymerase chain reaction, many copies of the extracted DNA are produced (PCR).

Step 3- DNA digestion by Restriction of Endonuclease Enzyme

The restriction endonuclease enzyme breaks down the DNA into smaller pieces. These enzymes cut the DNA at particular locations, chopping it up into different lengths.

Step 4- DNA Fragment Separation

Depending on their size, the DNA fragments are next separated using a process called electrophoresis.
In the presence of an electric field, a technique called electrophoresis is used to separate charged molecules. DNA fragments are positioned on a transparent gel bed on a plate for electrophoresis, which involves applying an electric current to the gel. DNA pieces gravitate toward the positive electrode because each one of their negative charges is unique. Eventually, the pieces and gel are distributed at various locations by their sizes.

Step 5

The agents that separate the DNA fragments into single strands are then introduced.

Step 6- Transferring (blotting) the isolated DNA fragments from the gel to synthetic membranes such as nylon or nitrocellulose

The isolated DNA fragments are then transferred from the gel to a nylon membrane or nitrocellulose, and this method is known as Southern blotting. In this method, the gel is coated with a nylon membrane that attracts the DNA fragments, much as how blotting paper dries wet ink.

Step 7- Radiolabeled Probe Hybridizations

In this stage, the radioactive isotope is added to the DNA fragments via hybridization so that their positions may be seen on an X-ray image. To accomplish this, a nylon membrane is added to a bath that contains probes (probes are short pieces of single standard complementary DNA, tagged with radioactivity that bind to a specific chain of DNA VNTR sequences according to the base-pairing rule).

Step 8- Hybridized DNA fragment detection

The membrane is exposed to the X-ray film to create an autoradiograph, which when developed reveals a distinctive pattern of dark and bright bands that reflect the makeup of DNA. The DNA fingerprints are represented by the dark bands on the X-ray film.

DNA Fragmentation



  1. Forensic Science: biological samples such as blood, hair, saliva, sperm, and body tissue cells are used for DNA profiling. It is possible to compare the DNA recovered from the evidence sample using the VNTR (Variable number of tandem repeats) prototype. It aids in the investigation of crimes like rape and murder.
  2. Personal Identification: It makes use of the idea that DNA fingerprints can be used to identify people, acting as a kind of genetic bar code.
  3. Determining Paternity and Maternity: A person accepts their VNTRs from their parents. Cases that were in disagreement have been resolved via parent-child VNTR prototype analysis. Additionally, immigration and inheritance proceedings may make use of this information.
  4. Breeding Program: Breeders typically assess a plant or animal’s genotype using its phenotype. Since homozygous or heterozygous dominance is difficult to distinguish from appearance, the genotype can be determined with great care and accuracy using DNA fingerprinting. Hunting dogs and racehorses can both benefit from it.
  5. Diagnosis of Hereditary Disorders: It can be used to identify inherited diseases in both newborn and prenatal children. Cystic fibrosis, hemophilia, Huntington’s disease, familial Alzheimer’s, sickle cell anemia, thalassemia, and a host of other conditions may fall under this category.
  6. The creation of treatments for inherited diseases: DNA prototypes linked to the disease can be identified by examining the DNA fingerprints of family members who have a history of a particular disorder.
  7. Detection of AIDS: A person with AIDS can be diagnosed by comparing the HIV “RNA” band (converted to DNA via RTPCR) with the bands formed by the man’s blood.

Issues that can happen in Forensic DNA Sample 

Degraded samples and DNA mixes are the two most frequent problems that forensic experts run against when examining DNA evidence.

Degraded DNA

Analyzing degraded DNA samples was nearly difficult until the development of contemporary PCR techniques. Techniques like RFLP, or restriction fragment length polymorphism High molecular weight DNA was necessary for the sample for restriction fragment length polymorphism, the first approach for DNA analysis in forensic science, to produce accurate results. However, high molecular weight DNA is not present in degraded samples because the DNA is too fragmented to perform RFLP with sufficient accuracy. Polymerase chain reaction analysis of degraded DNA samples was not possible before the development of contemporary PCR techniques. The little DNA snippets still present in damaged samples may be isolated and amplified, thanks in part to multiplex PCR. Multiplex PCR techniques differ significantly from more traditional techniques like RFLP. While RFLP required at least 100 ng of DNA to do an analysis, multiplex PCR has the potential to amplify less than 1 ng of DNA.

DNA Mixtures

When evaluating unknown or suspicious DNA samples, forensic scientists frequently run into the problem of mixtures. A DNA sample with two or more individual contributions is referred to as a mixture. This frequently happens when a DNA sample is taken from a substance that has been handled by multiple people or when a sample combines the DNA of the victim and the attackers. It can be difficult to identify individual profiles in DNA samples that contain multiple people, so only experts with extensive training should analyze mixtures will be challenging to analyze mixtures with two or three different individuals. The complexity of mixtures with four or more persons makes it impossible to obtain individual profiles. The proportion of DNA present in each individual, the genotype combinations, and the total amount of amplified DNA all play a significant role in how easily forensic scientists can interpenetrate DNA mixtures. The DNA ratio is frequently the most crucial factor to consider when figuring out whether a mixture can be interpreted. Fortunately, improvements in probabilistic genotyping may one day allow for this kind of conclusion. Probabilistic genotyping generates statistical likelihoods of individual genotypes detected in a mixture by putting thousands of mathematical computations through sophisticated computer software.

Restriction Enzymes

It is an enzyme that breaks DNA into small pieces at or close to particular recognition regions in molecules called restriction sites. Within the larger endonuclease group of enzymes, restriction enzymes are one subgroup. Restriction enzymes are often divided into five categories, which differ from one another in terms of their structure and whether or not they cleave DNA substrates at their recognition sites. Each sugar-phosphate backbone, or each strand of the DNA double helix, is cut by a restriction enzyme twice to cut DNA. While it is true that each person’s DNA is truly unique, there are some parts of your DNA that you have in common with everyone else on the earth. Since the sequence or order of certain bases is known, scientists have created molecules called restriction enzymes that hunt for those locations. As a result, when a scientist is examining someone’s DNA, they add restriction enzymes that locate those sites that everyone has and split the DNA strand in two. For all kinds of species, there are hundreds of restriction enzymes, and each one is designed to look for and cut a particular DNA sequence.

Short Tandem Repeats

Humans and other species have several different forms of identical DNA. The term “Short Tandem Repeat” or “STR” refers to the kind of DNA fingerprinting that is most frequently utilized. A portion of the human genome has been shown to have repeats of the same sequence, but with varying numbers of repetitions. Therefore, while the sequence “CAGT” may exist in all humans, its repetition rates may vary. It can be 10 times for you and 15 times for your neighbor. Researchers can recognize these minute variations and use them to uniquely identify you.

How are Restriction enzymes used in DNA Fingerprinting?

Short tandem repeats (STRs), a class of repeating components used in DNA fingerprinting, are examined in their pattern. STRs are non-coding DNA sequences that are located in the centromeric regions of chromosomes. STRs are therefore a subset of satellite DNA. Short nucleotide sequences (2–6 base pair) are therefore repeated sporadically in STRs. Since every person has a unique amount of STRs at a certain locus. Therefore, each person has a different DNA profile. In that regard, forensic investigations and paternity testing can both employ DNA fingerprinting to identify people.

How we can create a DNA profile using STR

Step 1: Get a sample of DNA

The majority of body cells, including white blood cells, semen, hair follicles, and body tissue, contain DNA. Because bodily fluids like saliva and sweat also include epithelial cells, DNA traces can be found there as well. DNA samples from crime scenes are collected by police personnel and forensic specialists. Additionally, a mouth swab can be used to harvest DNA straight from a person (which collects inner cheek cells)

Step 2: Extract the DNA

Cells’ nuclei are where DNA is located. To open the cells, extract the DNA, and separate it from other cell components, chemicals are used.

Step 3: Copy the DNA

The polymerase chain reaction (PCR) is used to repeatedly copy the STRs at each genetic locus to obtain sufficient DNA to create a profile because little amounts of DNA are frequently accessible for forensic investigation.

Step 4: Determine the size of the STR

A genetic analyzer is used to determine the size of the STRs at each genetic locus. The genetic analyzer can identify the fluorescent dye on each STR and uses gel electrophoresis to separate the replicated DNA. The identical apparatus is utilized in the lab for DNA sequencing.

Step 5: Is there a match?

The size of the STRs can be used to determine how many times a nucleotide sequence is repeated in each STR. This knowledge can be used by a forensic scientist to identify the source of a body fluid sample.

It is unlikely that two DNA profiles from distinct samples come from different individuals if they are identical. This offers solid proof that the samples came from the same source. Scientists look at STRs at 10 or more genetic loci to create a DNA profile. These genetic regions are typically located on various chromosomes.

FAQs on DNA Fingerprinting

Question 1: Define DNA profiling and name the father of Indian DNA fingerprinting.


The laboratory process known as DNA profiles uses the nucleotide sequences of particular regions of human DNA that are unique to each person to determine a person’s likely identification. The Father of Indian Fingerprinting is Dr. Lalji Singh.

Question 2: Write the principle on which DNA fingerprinting is based.


DNA fingerprinting or DNA profiling is the process of identifying the combination of DNA sequences that frequently differ considerably between individuals.

  • The most important prerequisite for DNA fingerprinting is the presence of short nucleotide repeats, which are inherited and differ in number from person to person. VNTRs, or variable number tandem repeats, are what these are.
  • The DNA fingerprinting method is based on the notion that only identical twins have the same DNA sequence (monozygotic twins).

Question 3: What are restriction enzymes and What is the full form of STRs?


A bacterial protein termed restriction enzyme, also known as restriction endonuclease, cleaves DNA at specified locations along the molecule. Restriction enzymes cleave foreign DNA inside the bacterial cell, killing off infected organisms. (Full form STRs are Short Tandem Repeats)

Question 4: Write about the application of DNA fingerprinting.


Application of DNA fingerprinting:

  • Forensic science
  • Breeding program
  • Detecting various diseases and their cures
  • Personal identification
  • Detection of AIDS
  • Determining paternity and maternity
  • Determining hereditary disorders.

Question 5: What are the main issues that can happen to DNA samples that can cause problems in DNA fingerprinting?


The two major issues faced in DNA fingerprinting are:

  • DNA mixture
  • DNA degradation

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Last Updated : 12 Oct, 2022
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