What is DNA Fingerprinting?

DNA Fingerprinting is a technique used to identify individuals by analyzing their unique DNA patterns. Studying the DNA Fingerprinting steps and process helps in understanding genetic relationships, solving crimes, and identifying individuals based on their unique DNA profiles.

In this article, we will cover DNA fingerprinting applications, uses, and steps. You can also find DNA fingerprinting notes here.

DNA fingerprinting is 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.

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

The labelled diagram of DNA Fingerprinting is given below:

The steps of DNA Fingerprinting are:

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 (PCR), many copies of the extracted DNA are produced.

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: Separation of DNA Fragments

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.

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).

The various applications of DNA Fingerprinitng are:

• 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 helps in the investigation of crimes like rape and murder.
• 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.
• Determining Paternity and Maternity: A person inherits their VNTRs from their parents. Cases of parentood disagreement can be resolved via parent-child VNTR prototype analysis. Additionally, immigration and inheritance proceedings may make use of this information.
• 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.
• 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.
• 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.
• 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.

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.

STR or small tandem repeats are used in DNA Profiling in the following ways:

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.

DNA fingerprinting is a powerful tool for identifying individuals based on unique DNA sequences. It is widely used in criminal investigations, paternity testing, and other forensic applications to match DNA samples from known and unknown individuals. The technique is also valuable in zoological, botanical, and agricultural studies. Invented by Sir Alec Jeffreys in 1984, DNA fingerprinting has since become a crucial method for solving crimes and determining biological relationships. Its applications extend to personal identification, diagnosing hereditary disorders, and even breeding programs, showcasing its versatility and importance in various scientific fields.

Also Read:

• What Is the Role of DNA in Heredity?
• DNA Replication
• Why is DNA Negatively Charged?

What is DNA Fingerprinting Explain?

DNA fingerprinting is a technique used to identify individuals by analyzing unique patterns in their DNA, focusing on specific regions called Short Tandem Repeats (STRs).

What is an Example of DNA Fingerprinting?

An example of DNA fingerprinting is its use in forensic science to match crime scene DNA with suspects or in paternity testing to determine biological relationships.

Who Discovered DNA Fingerprinting?

DNA fingerprinting was discovered by British geneticist Sir Alec Jeffreys in 1984.

What are the Principles of DNA Fingerprinting?

The principles of DNA fingerprinting include the uniqueness of an individual’s DNA sequence, the analysis of specific regions called STRs, and the comparison of these regions to identify or differentiate between individuals.

How does DNA Fingerprinitng Works?

DNA fingerprinting works by extracting DNA from a sample, amplifying specific regions using PCR, separating the fragments using gel electrophoresis, and comparing the resulting patterns to determine identity or relationships.