Question

Which of the following tools of recombinant DNA technology is incorrectly paired with its use

• A. EcoR I - production of sticky ends
• B. DNA ligase - multiplication of rDNA molecules
• C. DNA Polymerase - polymerase chain reaction (PCR) to amplify the DNA segments
• D. Selectable marker - identification of transformants

Answer 1

The correct option is B DNA ligase - multiplication of rDNA molecules

DNA ligase is an enzyme which joins or seals the gaps between DNA fragments by formation of phosphodiester bonds. It has no role to play in the multiplication of rDNA molecules.

EcoR I is a restriction endonuclease that recognises a specific palindromic sequence and makes cuts at these specific locations to form sticky ends in the DNA. The ends with single-stranded DNA “overhangs” are called sticky ends.

DNA polymerase enzyme helps in the synthesis of a DNA strand by adding deoxyribonucleotides to the 3' end of a primer. It is used in polymerase chain reactions (PCR) for amplifying the DNA segments.

Selectable markers are genes that help in identification and selection of transformants over non-transformants.

Transformants are those cells that have undergone genetic transformation through the uptake of foreign DNA.
Non-transformants are those cells which have not taken up the foreign DNA.

Generally, genes that confer resistance to organisms against antibiotics, serve as selectable markers.