Question

Molecular scissors: Restriction endonucleases :: Molecular glue: _________

• A. exonucleases
• B. DNA ligase
• C. RNA polymerase
• D. restriction enzymes

Answer 1

The correct option is B DNA ligase

Ligases are enzymes that are used to join two large molecules by forming a new chemical bond. For example, DNA ligase catalyses the joining of the 3′-OH to the 5′-phosphate, by forming a phosphodiester bond between two successive nucleotides.

Exonucleases are enzymes that cleave phosphodiester bonds in a polynucleotide chain from either the 5' or 3' end, one nucleotide at a time.

Endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain. Restriction enzymes are a type of endonuclease that are called molecular scissors as they cleave DNA at or close to specific recognition sequences of DNA known as restriction sites. These enzymes make a single incision on each of the two DNA strands and are also called restriction endonucleases.

RNA polymerase is an RNA synthesizing enzyme that transcribes RNA from DNA. It synthesizes the RNA strand in the 5' to 3' direction, while reading the template DNA strand in the 3' to 5' direction.