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Explain the importance of 'selectable marker' , with the help of a suitable example.

 

 

 

 
 
 
 
 

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The selectable marker helps in identifying and eliminating non-transformants and selectively permitting the growth of the transformants. B. Normally, the genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc., are considered useful selectable markers for E. coli. The normal E. coli cells do not carry resistance against any of these antibiotics.

Example- Selectable Markers in pBR322 pBR322, an E. coli cloning vector has two antibiotic resistance genes, i.e. for ampicillin and tetracycline. Antibiotic resistance is used as a selectable marker, i.e. it helps in the identification and selection of transformants. For example, when a foreign DNA is ligated at the site of tetracycline resistance (tet r ,) gene in pBR322, the recombinant plasmid will lose tetracycline resistance due to insertional inactivation of foreign DNA, but can still be selected out from nonrecombinants by placing the transformants on ampicillin containing medium. 

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Priyanka Kumari

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