Class 12 Biology Molecular Basis of Inheritance DNA fingerprinting

DNA fingerprinting

  • The process of comparison of DNA from different sources to establish the identity is called DNA fingerprinting.
  • DNA fingerprinting involves identifying differences in some specific regions in DNA sequence called as repetitive DNA.
  • Repetitive DNA are separated from bulk genomic DNA as different peaks during density gradient centrifugation.
  • The bulk DNA forms a major peak and the other small peaks are referred to as satellite DNA.
  • Satellite DNA is of two types based on base composition, length of segment, and number of repetitive units
  • micro-satellites
  • mini-satellites

Class_12_Molecular_Basis_Of_Inheritance_Satellite_DNA

Satellite DNA

  • Satellite DNA sequences normally do not code for any proteins, but they form a large portion of human genome.
  • Satellite DNA sequence show high degree of polymorphism and form the basis of DNA fingerprinting.
  • An inheritable mutation occurring in a population at high frequency, is referred to as DNA polymorphism.
  • Repeated nucleotide sequences in the non-coding DNA of an individual is called Variable Number of Tandem Repeats (VNTR).
  • The size of VNTR varies in size from 0.1 to 20 kb.
  • DNA fingerprinting includes the following steps
  • isolation of DNA
  • digestion of DNA by restriction endonucleases
  • separation of DNA fragments by electrophoresis
  • transferring (blotting) of separated DNA fragments to synthetic membranes, such as nitrocellulose or nylon.
  • hybridization using labelled VNTR probe
  • detection of hybridized DNA fragments by autoradiography.

Class_12_Molecular_Basis_Of_Inheritance_Fragments_Of_DNA

Fragments of DNA

Applications

  • In identification of criminals.
  • In determining population and genetic diversities.
  • In solving parental disputes.

Class_12_Molecular_Basis_Of_Inheritance_DNA_FingerPrinting

DNA fingerprinting in identification of criminals

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