Question

To prevent recirculation of vector DNA and to increase the frequency of production of recombinant DNA

• A. Reverse transcriptase is used
• B. Alkaline phosphatases are used
• C. Acid phosphatases are used
• D. All of them can be used

Answer 1

The correct option is B Alkaline phosphatases are used

Alkaline phosphatase removes 5' phosphate groups from DNA and RNA. It will also remove phosphates from nucleotides and proteins. These enzymes are most active at alkaline pH - hence the name.

There are two primary uses for alkaline phosphatase in DNA manipulations:

i) removing 5' phosphates from plasmid and bacteriophage vectors that have been cut with a restriction enzyme. In subsequent ligation reactions, this treatment prevents self-ligation of the vector and thereby greatly facilitates ligation of other DNA fragments into the vector (e.g., subcloning);

ii) removing 5' phosphates from fragments of DNA prior to labeling with radioactive phosphate.