Question

Stickiness of the ends of the DNA facilitates the

• A. Action of DNA ligase and these ends joined together laterally
• B. Action of Taq polymerase
• C. Action of restriction enzyme
• D. Action of DNA ligase and these ends joined together end-to-end

Answer 1

The correct option is D Action of DNA ligase and these ends joined together end-to-end

Sticky ends
Sticky end is a fragment of DNA produced by a staggered cut using restriction enzymes, in which the terminal portion has a stretch of unpaired nucleotides.

Formation of sticky ends
Formation of sticky ends is as follows:
When the restriction enzyme cuts DNA at one end of the sequence, between two bases on the same strand, then cuts on the opposite end of the complementary strand in the same way, sticky ends are produced.

Definition of DNA ligase
DNA ligase is the enzyme that creates the phosphodiester bond between the nucleotides of DNA fragments and joins them together.

Action of DNA ligase
Mechanism of action of DNA ligase is as follows:
When the sticky ends of the vector DNA and foregin DNA are added to each other, hydrogen bonds are formed between the complementary bases at the sticky ends. DNA ligase joins two DNA molecules (vector DNA and gene of choice) by catalyzing the formation of phosphodiester bonds of the nucleotides end-to-end, thus helping in the formation of recombinant DNA molecules.

Action of Taq polymerase
Taq polymerase is an enzyme isolated from Thermus aquaticus and is highly heat resistant. It catalyzes the synthesis of polynucleotides and is used for DNA amplification through the PCR technique.

Restriction endonuclease
Restriction endonucleases are the enzymes which cleave the DNA by digesting phosphodiester bonds at the specific sequences within the DNA. Examples include EcoR I.

Final answer
(B) Action of DNA ligase and these ends joined together end-to-end