DNA Fingerprinting

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  • DNA fingerprinting or DNA typing, is a DNA-based identification system that relies on genetic differences among individuals or organisms. 
  • Like fingerprints, every human has unique DNA; unlike fingerprints which can be surgically altered, one can’t change the DNA.
  • Fingerprint evidence can be too fuzzy to be read well, but DNA patterns are clear.

Procedure of DNA fingerprinting:

  1. Isolation of DNA: DNA must be recovered from the cells or tissues of the body. Only a small amount of tissue – like blood, saliva, semen, hair or skin.
  2. Cutting, sizing and sorting: Special enzymes called restriction enzymes are used to cut the DNA at specific places. The DNA pieces are sorted according to size by a sieving technique called electrophoresis. The DNA pieces are passed through a gel made from sea weed agarose.
  3. Transfer of DNA to nylon: The distribution of DNA pieces is transferred to a nylon sheet by placing the sheet on the gel and soaking them overnight.
  4. Probing: Adding radioactive or coloured probes to the nylon sheet produces a patterns called the DNA fingerprint. Each probe typically sticks in only one or two specific places on the nylon sheet.
  5. DNA fingerprint: The final DNA fingerprint is built by using several probes (5-10 or more) simultaneously. The segments marked with probes are exposed on X-ray fil, where they form a characteristic pattern of black bars – the DNA fingerprint.

Applications of DNA fingerprinting

  1. Forensic Uses: In criminal investigations, DNA from samples of hair, bodily fluids or skin at a crime scene is compared with those obtained from suspected perpetrators.  DNA typing is also used to identify the remains of unknown individuals, as in the identification of the soldiers, or to identify the bodies of people killed in political violence or accidents whose bodies are unrecognizable.
  2. Paternity: Paternity determination is possible with DNA typing because half of the father’s DNA is contained in the child’s genetic material. 
  3. Anthropology: DNA fingerprinting has also been used extensively to identify human remains, solving long-standing mysteries. DNA has had an enormous impact on anthropology as well.
  4. Wildlife Management: The more the genetic makeup of natural populations is understood, the better conservation and management plans will be.
Practice Questions
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