Gene Isolation

  1. Describe stage 1 of gene isolation
    The fragment of DNA containing the desired gene is obtained
  2. Describe stage 2 of gene isolation
    The DNA is cut into fragments using a restriction endonuclease
  3. Describe stage 3 of gene isolation
    The solution of DNA fragments is placed in wells of agarose gel across which an electrical current is applied
  4. Describe stage 4 of gene isolation
    • The DNA is negatively charged due to the phosphate groups 
    • This means it moves towards the positive electrode
  5. Describe stage 5 of gene isolation
    • The smaller DNA fragments move more quickly through the gel than the large fragments 
    • This means they will soon separate on the basis of their length
  6. Describe stage 6 of gene isolation
    • The gel can be stained to show up the position of the DNA fragments 
    • This is compared to the positions of DNA of known length
  7. Describe stage 7 of gene isolation
    • In order to identify a particular fragment, a DNA probe is used 
    • The probe is a short, single stranded piece of DNA complementary to the desired sequence 
    • The probe binds to the sequence in a process of hybridisation 
    • If the probe is composed of radioactive nucleotides or attached to a fluorescent molecule it will identify the fragment
  8. Describe stage 8 of gene isolation
    • An unexposed photographic film is laid on the gel once the gel has run 
    • The radioactive fragments will create dark shadows on the film corresponding to the positions of the DNA fragments in the gel 
    • This is known as autoradiography
  9. Describe stage 9 of gene isolation
    The pattern of bands on the gel produced by the different sized fragments is called the restriction map and will depend on the type of restriction endonuclease added as each type cuts the DNA at a specific base sequence
Card Set
Gene Isolation
AQA BIOL5 Gene isolation