Question

Synthesis of DNA can be stopped by incorporating artificial

• A. ddATP
• B. ddGTP
• C. ddCTP
• D. All of the above

Answer 1

The correct option is D All of the above

• Primer is a stranded segment (complementary to the template) and has a free 3’ hydroxyl group to facilitate the addition of nucleotides by polymerase enzymes.
• DNA polymerase catalyzes the formation of the phosphodiester linkage between 3’ hydroxyl group of primer and $\alpha$-phosphate of the incoming nucleoside triphosphate.
• Dideoxyribonucleotide triphosphates (ddNTP) are modified nucleotide that has the same structure as a normal dNTP but with the exception of the 3' OH group being replaced by an H; thus not providing the free 3’OH group.
• DNA polymerase senses the presence of modified monomers and immediately stops DNA synthesis.
• As termination of DNA synthesis is due to the absence of free 3’ OH group, any of four modified nucleotides produce the same effect.

Thus, the correct answer is option D.