Question

If a nucleotide lacking a hydroxyl group at the 3' end were added to a pcr reaction, what would be the outcome?

a. strand elongation would proceed as normal.
b. no additional nucleotides would be added to a growing strand containing that nucleotide.
c. nucleotides would only be added at the 5's end.
d. t. aquaticus dna polymerase would be denatured.

Answer 1

The correct answer is b. no additional nucleotides would be added to a growing strand containing that nucleotide.

Nucleotides without a 3’hydroxy group are called dideoxynucleotides (ddNTD). Dideoxynucleotides are inhibitors of DNA polymerase because after being added in PCR reaction no further nucleotides can be added as no phosphodiester bond can be created (usually 3' hydroxyl group of the previous nucleotide attaches to 5' phosphate of the current nucleotide).