Context: 

DNA Fingerprinting has become the most often used tool to verify the biological identity of any person. 

About DNA and its use in profiling:

• DNA (Deoxyribonucleic Acid) is the genetic material found in cells, consisting of 46 chromosomes (23 inherited from each parent). It is packed inside the chromosomes. 
• It contains a genetic blueprint of an individual, making it a powerful tool for biological identification.
• It is incredibly stable and can be preserved for thousands of years. For instance, scientists have extracted usable DNA from remains that are 65,000 years old.
• This stability makes it a reliable tool for forensic investigations even in cases involving historical remains or archived materials.
• Polymorphisms in DNA sequences are used to differentiate individuals and trace their ancestry, allowing for the creation of DNA profiles.
• DNA profiles are typically generated using polymorphisms in parts of the DNA called short tandem repeats (STRs).

Short Tandem Repeats (STRs):

• DNA consists of four chemical bases (adenine, cytosine, guanine, and thymine), which form complementary pairs.
• STRs (Short Tandem Repeats) are repeating short sequence of base-pairs on the DNA, that vary in number between individuals. 
• These regions are often polymorphic, making them highly useful for distinguishing between unrelated individuals.
• STR analysis is a key method for creating DNA fingerprints used in forensic investigations.

Polymerase Chain Reaction (PCR) for DNA Amplification:

• To study DNA in detail, scientists use Polymerase Chain Reaction (PCR) to create multiple copies of specific DNA segments.
• PCR involves heating DNA to separate its strands, using primers to target specific sequences, and synthesizing new strands with the help of DNA polymerase.
• This process allows scientists to amplify even small samples of DNA, making it easier to analyse STRs and create DNA fingerprints.

DNA Fingerprinting:

Once DNA is amplified, it can be analysed using capillary electrophoresis, a method that separates DNA fragments based on size under an electric field.

• New copies of DNA can be made to move through a capillary under the influence of an electric field. 
• Multiple STRs can simultaneously be sized in the same test.

DNA fingerprints are generated by analysing the size of various STRs, producing a unique profile for each individual.

Applications of DNA Fingerprinting:

• Forensic investigations: DNA from crime scenes (blood, sweat, saliva) helps identify suspects and link them to criminal activities.
• Parent/child identification: DNA fingerprints are crucial in establishing biological relationships, especially in cases involving disputes or verification.
• Exoneration of wrongfully convicted individuals: DNA evidence has been used to overturn unjust convictions by providing conclusive proof of innocence.
• Organ transplantation: DNA fingerprints are used to ensure compatibility between organ donors and recipients.

Significance of DNA Fingerprinting:

• It has revolutionized the field of forensics and criminal justice by providing an objective, scientifically-backed method of identifying individuals.
• It has become a crucial part of both criminal and civil law, contributing to accurate identification, crime resolution, and ensuring justice in numerous cases.