isn't it the plasmid dna that contains the antibiotic resistance genes,then how will we identify the recombinant dna from the non recombinants by culturing them in antibiotic medium?

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Solution

The recombinant DNA contains a specific antibiotic resistant gene (e.g, gene for ampicillin resistance) called selectable marker gene. when this rDNA is introduced in the host cell say E.coli. Then E. coli is cultured in a medium containing antibiotic (ampicillin), only cells containing recombinant DNA will be able to survive due to antibiotic (ampicillin) resistance genes. The other cells that do not contain recombinant DNA will not be able to survive because of lack of antibiotic resistant gene (Ampicillin) and one will be able to isolate the recombinants from non recombinants.

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