The genes encoding resistance to antibiotics are cosidered useful selectable markers because the normal £. coli cells do not carry resistance against any of these antibiotics.
Example A foreign DNA is ligated at the Bam HI site of tetracycline resistance gene in the vector pBR322. The recombinant plasmids will lose tetracycline resistance due to the insertion of foreign DNA but can still be selected from non-recombinants by plating the transformants on ampicillincontaining medium.
The transformants growing on ampicillin containing medium are then transferred on medium containing tetracycline. The recombinants will not grow, while non- recombinants will grow on the medium containing both the antibiotics. Antibiotic resistance gene, thus helps in selecting the transformants.
Why are genes encoding resistance of antibiotics considered useful selectable markers for coli cloning vector? Explain with the help of one example.
Answers
Prasad karnatka
The genes encoding resistance to antibiotics are cosidered useful selectable markers because the normal £. coli cells do not carry resistance against any of these antibiotics.
Example A foreign DNA is ligated at the Bam HI site of tetracycline resistance gene in the vector pBR322. The recombinant plasmids will lose tetracycline resistance due to the insertion of foreign DNA but can still be selected from non-recombinants by plating the transformants on ampicillincontaining medium.
The transformants growing on ampicillin containing medium are then transferred on medium containing tetracycline. The recombinants will not grow, while non- recombinants will grow on the medium containing both the antibiotics. Antibiotic resistance gene, thus helps in selecting the transformants.