Question
How do antibiotic-resistance genes function as selectable markers? Explain with the help of E.coli cloning vector pBR 322.
✓
Answer
- If a foreign DNA is ligated at the BamH I site of tetracyclin-resistance gene in the pBR 322, the recombinant plasmid will lose the tetracycline-resistance.
- The transformant can be selected out from the nontransformants by culturing on a medium containing ampicillin.
- The transformants are transferred to a culture medium containing tetracyclin; there they fail to grow but non-transformants grow in tetracyclincontaining medium as well as ampicillin-containing medium.
- Here, one antibiotic gene facilitates selection of transformants, while the other antibiotic gene gets inactivated by the insertion of alien DNA and facilitates selecting the recombinants.
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