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DNA fingerprinting

  Apr 13, 2023

DNA fingerprinting

Q What is DNA fingerprinting?

  • DNA fingerprinting was first developed in 1984 by Alec Jeffreys in the UK, after Jeffreys discovered that no two people could have the same DNA sequence.
  • Within three years of the discovery, the UK achieved the world’s first conviction based on DNA evidence in a case of rape and murder.


Q How is DNA fingerprinting done?

  • Each person’s DNA, except for identical twins, is unique.
  • By analyzing selected DNA sequences (called loci), a crime laboratory can develop a profile to be used in identifying a suspect.
  • DNA can be extracted from many sources, such as hair, bone, teeth, saliva, and blood.
  • Because there is DNA in most cells in the human body, even a minuscule amount of bodily fluid or tissue can yield useful information.
  • Samples may even be extracted from used clothes, linen, combs, or other frequently used items.


Q What is DNA ? 

Deoxyribonucleic Acid (DNA)

  • DNA is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA.
  • Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).
  • Mitochondria are structures within cells that convert the energy from food into a form that cells can use.
  • The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T).
  • Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people.

The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.



Q How it is used in criminal investigation?

  • DNA evidence is used to solve crimes in two ways:
  1. If a suspect is known, that person’s DNA sample can be compared to biological evidence found at a crime scene to establish whether the suspect was at the crime scene or whether they committed the crime.
  2. If a suspect is not known, biological evidence from the crime scene can be analyzed and compared to offender profiles in existing DNA databases to assist in identifying a suspect.
  • Beyond its accuracy, DNA fingerprinting can also sift through crime scene evidence in different ways, previously unavailable to investigators.
  • For instance, advanced DNA fingerprinting can make separate prints of various individuals even from a sample mixture found at the crime scene — this is of help during gang rape investigations as each perpetrator can be individually identified.


Q What is status of DNA fingerprinting in India ?

  • By 1988, Lalji Singh, who had been in the UK from 1974 to 1987 on a Commonwealth Fellowship, developed DNA fingerprinting for crime investigations in Hyderabad.
  • Today, Lalji Singh, who passed away in 2017, is known as “the father of DNA fingerprinting in India.”
  • In 1989, DNA fingerprinting was first used in a case by the Kerala Police.
  • By the early 1990s, the technology had begun to be used for establishing paternity, and to link criminals and identify victims in sensational crimes.
  • From the 2000s onwards, the technology became a staple in rape cases where vaginal swab samples were matched with semen samples from suspects.


Q What are the challenges with DNA fingerprinting in India ?

  • It is vital to ensure that the DNA of the investigators does not get mixed with that of the victims or the suspects.
  • Thus, picking up samples from a crime scene with sterile tools and storing samples in a proper manner are crucial for the evidence to stand a judicial test.
  • While India has rules and guidelines regarding this, India’s police forces have a lot of catching up to do with counterparts overseas.
  • While central agencies such as CBI have the expertise to ensure that crime scenes are protected and correct procedure is followed, state police forces are inadequately trained or fully equipped.


Q What are the Issues with such technology ?


  • The problem is not limited to the police awareness.
  • The capacity for DNA fingerprinting in the country itself is lacking.
  • DNA fingerprinting is available only at a few places — Maharashtra, West Bengal, Delhi, Hyderabad and Chandigarh.
  • Advanced practices in the technology are limited to the Centre for DNA Fingerprinting and Diagnostics (CDFD) in Hyderabad.