Question
  1. Why are engineered vectors preferred?
  2. A vector is engineered with three features, which facilitate its cloning within the host cell. List the three features and explain each one of them.

Answer

  1.  
  1. Engineered vectors help easy linking of foreign DNA.
  2. They facilitate selection of recombinants from non-recombinants.
  1. Features of Cloning vectors:
  1. Origin of Replication (Ori):
  • This is the sequence of DNA from where replication starts.
  • Any piece of alien/ foreign DNA linked to it is made to replicate within host cell; it also decides the copy number of the linked DNA.
  1. Selectable marker: A marker is a gene, which helps in selecting the host cells, which are transformants/ recombinants from the non-recombinant ones, eg ampicillin and tetracycline resistant genes in E.coli
  2. Cloning site: The vector should have a few, preferably one unique recognition site to link the foreign DNA, presence of a particular cloning/ recognition site enables the particular restriction enzyme to cut the vector DNA.

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