1-2.1 Recombinant DNA:

• Single chimeric DNA formed by combining two or more different fragments of DNA from diverse organisms is generally called as recombinant DNA and the method applied to create recombinant DNA is called recombinant DNA technology.
  
  
• The organism, from which the candidate DNA is isolated, is called Donor organism. The organism which will accept the foreign gene is called Host organism.
  
  
• Genetic material from one organism is selected and then artificially introduced to a host organism. if the foreign recombinant DNA integrates into the host genome, it gets replicated along with the genome and then express the foreign protein.
  
  
• Paul Berg, Herbert W. Boyer and Stanley N. Cohen are the pioneers of recombinant DNA technology (early 1970).
  
  
• A hybrid of the SV40 mammalian DNA virus genome and phage λ was one of the recombinant DNA molecules to be first engineered.
  
  
• There are three approaches to make recombinant DNA:

  1. Transformation
  2. Non- bacterial transformation/transfection
  3. Phage introduction/transduction

Transformation:

Transformation is direct uptake of exogenous DNA via cell membrane leading to incorporation into the host DNA. It is commonly occurred in bacteria. Transformation requires different tools of molecular biology to insert foreign DNA into the host. For example, vector to carry the foreign DNA to the host; restriction enzymes to cut the DNA in specific site; ligase to join two DNA molecule etc.

Non-bacterial transformation/transfection:

The process of foreign DNA uptake by host cell driven by mechanical or chemical factors is classified under non-bacterial transformation, also termed as transfection. Different methods of non-bacterial transformation are microinjection, liposome mediated transformation, biolistics etc.