Gene Cloning:

• The production of a large population of a DNA fragment in pure form is called as gene cloning.
• It involves the formation of recombinant DNA and its introduction into the mother bacterial cell.
• The recombinant DNA is formed by combining DNAs from two different organisms.
• This process is called genetic engineering. A DNA fragment of one organism (called as Passenger DNA) is transferred into another organism by combining it with another DNA(called as Vehicle DNA).
• Normally plasmid or bacteriophage DNA is used as Vehicle DNA. Both the passenger and vehicle DNA are cleaved by using restriction endonuclease enzyme and they are mixed under suitable conditions.
• Their complementary sticky ends pair and their ends are sealed by ligase enzyme. The resulting DNA is called recombinant DNA.
• The recombinant DNA is added to the culture containing growing host bacteria.
• These bacteria take the recombinant DNA along with the nutrients.
• This DNA replicates when the bacteria divide and produce a large clone of recombinant DNA.