DNA Fingerprinting Technology: Steps, Types & Applications

DNA fingerprinting is one of the forensic methods used for identification purposes on special DNA patterns. It is important because it has so many areas in which it is applied, such as in legal investigations of crimes, patria cases, and for corpse identifications. This article aims to probe in detail the processes, types, and applications of this technology.

What is DNA Fingerprinting?

• DNA Fingerprinting is one forensic tool that is commonly used for identifying persons based on their DNA patterns.
• A complementary point here is that each individual, except a set of identical twins, has unique DNA composed of different-combination nucleotide sequences.
• From its forensic uses of crime-solving, paternity determination to unknown human remains identification, DNA fingerprinting has many applications.

Key Steps in DNA Fingerprinting

Here is a DNA Fingerprinting process:

• Sample Collection: A biological sample from the crime scene or the individuals involved or any other relevant source is collected. Blood, saliva, semen, hair, and tissues are common types of samples.
• DNA Extraction: To extract the DNA, an appropriate technique is selected according to the nature of the sample. In general, a cell lysis procedure to separate the DNA from cells and protein digestion with protease enzymes to remove contaminating proteins are applied. Extracted DNA is usually in a mixture with other cell components.
• DNA Purification: The isolated DNA undergoes purification to eliminate contamination from proteins, etc. This purification provides clean DNA that is very important in further analysis.
• Polymerase Chain Reaction: Here, certain short regions of DNA known as short tandem repeats (STRs) or variable number tandem repeats (VNTRs) are targeted for selective amplification. These regions are highly polymorphic. Hence the differences between two or more individuals in these regions are measured by PCR. Even if a small amount of DNA or degraded DNA is left, PCR can still amplify the DNA.
• Gel Electrophoresis: This technique is used to separate DNA of varying length after it has been amplified through the process of PCR.
• A gel containing tiny pores separates the DNA fragments based on their length. Smaller fragments move faster through the gel, while larger fragments move more slowly.
• DNA Visualization: After electrophoresis, the DNA fragments separated are visualised by radiation techniques or stains (e.g., ethidium bromide).
• The fragments thus make up a pattern of bands on the gel.
• Pattern Analysis: The DNA-fragment pattern, often called the DNA “fingerprint,” is analysed.
• The number and size of the fragments at particular STR loci are compared between unknown samples and reference samples of the known identity (e.g., suspects or victims).
• Matching: A positive match occurs whereby the DNA fingerprint from an unknown sample coincides with the DNA fingerprint of a known individual.
• The result can thus be utilised in criminal investigations, paternity, and other cases.
• Statistical Analysis: Statistics are indeed calculated to show the strength of the match, enabling one to express association in terms of the likelihood of the two DNA profiles being contributed by either the same individual or unrelated individuals.

Types of DNA Fingerprinting

The types of DNA Fingerprinting are as follows:

Some of the primary types of DNA fingerprinting methods:

• Short Tandem Repeat (STR) Profiling: STR profiling is one of the most commonly used DNA fingerprinting methods in forensics and paternity testing.
  • It analyses specific regions of DNA containing short repeated sequences (e.g., 4-6 base pairs). 
  • The number of repeats varies among individuals, creating a unique STR profile. STR profiling is highly sensitive and can be used with degraded DNA samples.
• Variable Number Tandem Repeat (VNTR) Analysis: VNTR analysis was one of the earliest DNA fingerprinting methods.
  • It analyses regions of DNA containing longer repeating sequences (e.g., 10-100 base pairs). 
  • The number of repeats at each VNTR locus is highly variable between individuals. 
  • Although less commonly used today, VNTR analysis played a crucial role in the early development of DNA fingerprinting.
• Single Nucleotide Polymorphism (SNP) Profiling: SNP profiling examines single nucleotide variations at specific positions in the genome. SNPs are the most common type of genetic variation in humans.
  • SNP profiles are used in genetic research, population genetics, and some clinical applications.
• Mitochondrial DNA (mtDNA) Analysis: Mitochondrial DNA is inherited solely from the mother and contains unique genetic markers.
  • MtDNA analysis is often used in forensic cases where nuclear DNA is degraded or unavailable. 
  • It is also used to track maternal lineages and study ancient DNA.
• Y-Chromosomal DNA Analysis: This technique analyses specific regions of the Y chromosome.
  • It is advantageous in paternity testing and ancestry research, as the Y chromosome is passed from father to son, allowing the tracing of paternal lineages.
• Amplified Fragment Length Polymorphism (AFLP): AFLP is a technique that generates DNA fingerprints by selectively amplifying and analysing specific fragments of genomic DNA. It has applications in genetic diversity studies and plant breeding.
• Restriction Fragment Length Polymorphism (RFLP): RFLP analysis involves digesting DNA with restriction enzymes and separating the resulting fragments by size through gel electrophoresis.
  • Variations in the number and location of restriction sites lead to unique RFLP patterns. 
  • While an early DNA fingerprinting method, it has mainly been replaced by more modern techniques.
• Digital PCR (dPCR): Digital PCR is a quantitative method for absolute quantification of DNA fragments.
  • It is used in some applications where precise quantification is crucial, such as detecting rare alleles or low-abundance genetic markers.
• Whole Genome Sequencing (WGS): While not a traditional DNA fingerprinting method, WGS involves sequencing an individual’s genome.
  • The resulting sequence data can generate a comprehensive and highly informative genetic profile.

Read our detailed article on Genetics.

Applications of DNA Fingerprinting

The application of DNA Fingerprinting can be seen as follows:

• Criminal Investigations: DNA fingerprinting is frequently used, in criminal justice, to link suspects to crime scenes or to exclude innocents. It can identify perpetrators of crimes such as murder, sexual assault, burglary, and kidnapping.
• Paternity Testing: Such testing determines such fatherhood and motherhood through the DNA fingerprinting technique. This is crucial when up for child custody rights and inheritance matters, and it establishes responsibilities legally.
• Missing Persons and Unidentified Remains: DNA profiling identifies missing persons in cases of accidents, natural disasters, or criminal cases. It may assist in identifying remains in mass graves or long-identified deceased individuals.
• Immigration and Citizenship: DNA fingerprinting can establish biological relationships in immigration cases whereby individuals seek to join their family members in another country or to endeavor to gain citizenship with regard to family ties.
• Forensic Genealogy: Advances in DNA fingerprinting methods, now aided by genealogical databases, have become a solution to tracing distant relatives in cold cases and, thereby, in many cases, identifying suspects or victims. 
• Conservation of Wildlife: Attaining DNA profiles is taken into consideration while studying and surveying wildlife populations, tracing the illegal trade of endangered species, and combating poaching. It helps to identify individuals within a species so as to conserve them, measure genetic variation, and recommend conservation plans. 
• Farming and Animal Husbandry: Agricultural DNA fingerprinting aids food authentication in its simplest form, detection of food fraud, and tracing of livestock for breeding and quality evaluation assignment purposes. 
• Historical and Anthropological Research: DNA fingerprinting aids in studying ancient DNA to establish human migration patterns, ancestry, and evolution; it can also be extrapolated into solving historic enigmas and identifying the remains of historians. 
• Disaster Victim Identification (DVI): In cases of mass disasters such as an air crash or natural disasters, fingerprinting is used for identifying the victim when there is no chance for other methods (like visuals) being available.
• Genealogical Research: Individuals interested in tracing their ancestry and genealogy can use DNA fingerprinting services to discover their genetic heritage and locate distant relatives.
• Consanguinity Testing: DNA fingerprinting can establish the degree of consanguinity (kinship) between individuals and determine if they share common ancestors, which can be relevant in legal matters and medical genetics.
• Quality Control in Biotechnology: DNA fingerprinting is used in biotechnology and pharmaceutical industries to verify the authenticity and purity of cell lines, microbial strains, and DNA samples.

Conclusion

In conclusion, DNA fingerprinting has transformed how we approach identification and forensic analysis, offering powerful applications across diverse fields. Its ability to link individuals to specific events, resolve familial disputes, and contribute to conservation efforts highlights its significance in modern science. As technology continues to evolve, the precision and reliability of DNA fingerprinting are expected to improve further, solidifying its role as a critical tool in justice, research, and beyond.

FAQs: DNA Fingerprinting Technology

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