Question

pBR322 is frequently used as a vector in biotechnology. It helps in cloning foreign genes of interest. Which of the following is the correct statement about this vector?

• A. It has three antibiotic resistance genes
• B. It contains the restriction site for Sal I within the tetracycline resistance gene
• C. It occurs naturally in Escherichia coli
• D. Both b and c

Answer 1

The correct option is B It contains the restriction site for Sal I within the tetracycline resistance gene

In biotechnology, vectors are molecules which act as vehicles to carry genes of interest (GOI) into the host organism.

The plasmid pBR322 is not a naturally occurring plasmid in E.coli. It is an artificial cloning vector constructed by Bolivar and Rodriguez.

In pBR322, p stands for Plasmid, B for Bolivar, R for Rodriguez and 322 is the number given to this plasmid to distinguish it from other vectors they developed in their laboratory.

It has two antibiotic resistance genes - one against the antibiotic tetracycline and another against the antibiotic ampicillin.

The specific DNA sequences which are recognized by the restriction enzymes are called restriction sites (recognition sites). It has various restriction sites which are specific DNA sequences within which restriction endonucleases cleave phosphodiester bonds and create DNA fragments. The restriction sites for Sal I and BamH I lie within the tetracycline resistance gene.