16.2 - In vivo gene cloning - the use of vectors

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Cloning the fragments

  • in vivo, by transferring the fragments to a host cell using a vector
  • in vitro, using the polymerase chain reaction

Once the complementary base pairs of two 'sticky ends' pair up, DNA ligase joins the phosphate-sugar framework. 

PLASMID - used as a vector to transport DNA into host cell

Plasmids and bacterial cells are mixed together in a medium containing calcium ions. The calcium ions and changes in temperature  make the bacteria permeable, allowing the plasmids to pass through the cell membrane into the cytoplasm. However, not all the bacterial cells will possess the DNA fragments because:

  • only a few bacterial cells (1%) will take up the plasmids when mixed
  • some plasmids will have closed again without incorporating the DNA fragment

To find out which carry genes for antibiotic resistance e.g. ampicillin

  • all the…

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