Final answer:
At the 3' end of a DNA strand, there is a hydroxyl group. This is due to the formation of phosphodiester bonds between the 5' phosphate of one nucleotide and the 3' hydroxyl group of the next nucleotide in the DNA polymer.
Step-by-step explanation:
The chemical group at the 3' end of a DNA strand is known as the hydroxyl group. When nucleotides form the DNA polymer, they connect through phosphodiester bonds. These bonds are established between the 5' phosphate group of one nucleotide and the 3' hydroxyl group of the adjacent nucleotide. As a result of this pattern of bonding, every DNA strand has a free phosphate group at the 5' end and a free hydroxyl group at the 3' end.
In summary, the backbone of DNA is composed of sugar and phosphate groups, while the bases extend from this backbone. It's essential to remember the antiparallel arrangement of DNA strands, with one running 5' to 3' and the opposite strand running 3' to 5', each strand complementary to the other due to the specific base pairing (Adenine with Thymine, and Guanine with Cytosine in DNA).