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Genetic Fingerprinting
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Genetic Fingerprinting

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  • Introns are non-coding.
    Exons code for the proteinbiosynthesis.
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  • 1. Genetic fingerprinting Each DNA profile is unique!
  • 2. Genetic fingerprinting
    • Regions of chromosomes that code for proteins are called introns .
    • Other regions that are non-coding are called extrons.
  • 3. Genetic fingerprinting
    • Extrons contain blocks of repeated nucleotides called short tandem repeats (STRs)
    • It is the number of times that these STRs are repeated that produces the variations in individuals.
  • 4. Genetic fingerprinting
  • 5. How it is done – part 1
    • DNA is extracted from sample.
    • Cut into millions of small fragments
    • Using restriction endonucleases
    • Aimed at STRs
  • 6.  
  • 7. How it is done – part 2
    • DNA fragments are separated by electrophoresis
    • (Fragments are exposed to electric current in a trough of gel)
    • Different fragments move at different rates through the gel.
  • 8. How it is done – part 2
    • The smaller the fragment – the faster it moves.
    • DNA is separated into bands according to size of the fragments.
  • 9. How it is done – part 3
    • The pattern of fragments are transferred to a nylon membrane by a process called Southern blotting .
  • 10. How it is done – part 4
    • Radioactive probes are used to attach to specific parts of the fragments.
    • Any probes not bound are washed off.
    • The membrane is dried
  • 11. How it is done - part 5
    • The nylon sheet is placed under X-ray film.
    • The radioactive probes on the DNA fragments expose the film.
    • This produces visible pattern of light and dark bands which is unique to each individual.