Question

The polarity in a DNA strand is indicated by referring to one end as the 3′ end

and the other as the 5′ end. Which structure is on the 3′ end?
A. Hydroxyl group
B. Phosphate group
C. Nitrogenous base

Answer 1

The 3' end of a DNA strand contains a free hydroxyl group, and this is where DNA polymerization continues, adding new nucleotides.

Step-by-step explanation:

The 3' end of a DNA strand has a free hydroxyl group (-OH). In the DNA structure, the sugar-phosphate backbone is formed by the sugar molecules and phosphate groups of each nucleotide. The phosphodiester bonds link the 5' phosphate group of one nucleotide to the 3' hydroxyl group of the next. This creates a directional or polar strand with a 5' end, which has a free phosphate group, and a 3' end with a free hydroxyl group. Therefore, the correct answer to the question of which structure is on the 3' end is A. Hydroxyl group.